Merge pull request #20 from zachd/feat-calendar-start-date-c6a9d

Add start dates

package.json

@@ -7,16 +7,21 @@
 		"build": "vite build",
 		"preview": "vite preview",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
-		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch"
+		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
+		"test": "vitest run",
+		"test:watch": "vitest",
+		"test:ui": "vitest --ui"
 	},
 	"devDependencies": {
 		"@sveltejs/adapter-auto": "^3.0.0",
 		"@sveltejs/kit": "^2.0.0",
 		"@sveltejs/vite-plugin-svelte": "^4.0.0",
+		"@vitest/ui": "^4.0.8",
 		"svelte": "^5.0.0",
 		"svelte-check": "^4.0.0",
 		"typescript": "^5.0.0",
-		"vite": "^5.0.3"
+		"vite": "^5.0.3",
+		"vitest": "^4.0.8"
 	},
 	"dependencies": {
 		"date-holidays": "^3.23.12",

src/lib/CalendarMonth.svelte

@@ -8,6 +8,8 @@
     export let consecutiveDaysOff: Array<{ startDate: Date; endDate: Date; totalDays: number }>;
     export let selectedCountryCode: string;
     export let weekendDays: number[] = [6, 0];
+    export let startDate: Date = new Date(year, 0, 1);
+    export let isActive: boolean = true;
 
     // Function to determine the first day of the week based on locale
     function getFirstDayOfWeek(locale: string): number {
@@ -84,12 +86,19 @@
         return weekendDays.includes(date.getDay());
     }
 
+    function isPastDate(day: number): boolean {
+        const date = new Date(year, month, day);
+        // Normalize startDate to current year for comparison
+        const startDateInYear = new Date(year, startDate.getMonth(), startDate.getDate());
+        return date < startDateInYear;
+    }
+
     const dayInitials = ['S', 'M', 'T', 'W', 'T', 'F', 'S'];
 
     $: orderedDayInitials = dayInitials.slice(firstDayOfWeek).concat(dayInitials.slice(0, firstDayOfWeek));
 </script>
 
-<div class="calendar">
+<div class="calendar {isActive ? '' : 'excluded-month'}">
     <div class="month-name">{new Date(year, month).toLocaleString('default', { month: 'long' })}</div>
     
     {#each orderedDayInitials as dayInitial}
@@ -101,7 +110,8 @@
     {/each}
     {#each Array.from({ length: daysInMonth }, (_, i) => i + 1) as day}
         {@const holiday = getHoliday(day)}
-        <div class="day {isWeekend(new Date(year, month, day)) ? 'weekend' : ''} {holiday ? 'holiday' : ''} {isOptimizedDayOff(day) ? 'optimized' : ''} {isConsecutiveDayOff(day) ? 'consecutive-day' : ''}">
+        {@const pastDate = isPastDate(day)}
+        <div class="day {isWeekend(new Date(year, month, day)) ? 'weekend' : ''} {holiday ? 'holiday' : ''} {isOptimizedDayOff(day) ? 'optimized' : ''} {isConsecutiveDayOff(day) ? 'consecutive-day' : ''} {pastDate ? 'past-date' : ''}">
             <span class={holiday?.hidden ? 'strikethrough' : ''}>{day}</span>
             {#if holiday}
                 <Tooltip text={holiday.name} />
@@ -137,6 +147,14 @@
         color: #c5c6c7;
         font-size: 0.6em;
     }
+
+    .excluded-month .month-name {
+        color: #666;
+    }
+
+    .excluded-month .day-initial {
+        color: #666;
+    }
     .day {
         aspect-ratio: 1;
         text-align: center;
@@ -202,4 +220,12 @@
         text-decoration: line-through;
         opacity: 0.5;
     }
+
+    .past-date {
+        opacity: 0.4;
+    }
+
+    .past-date span {
+        text-decoration: line-through;
+    }
 </style> 

src/lib/holidayUtils.test.ts

@@ -0,0 +1,781 @@
+import { describe, it, expect, beforeEach, vi } from 'vitest';
+import { getHolidaysForYear, optimizeDaysOff, calculateConsecutiveDaysOff } from './holidayUtils';
+
+// Test constants
+const TEST_YEAR = 2024;
+const DEFAULT_WEEKENDS = [0, 6]; // Sunday, Saturday
+const CUSTOM_WEEKENDS = [5, 6]; // Friday, Saturday
+
+// Mock browser APIs
+const mockNavigator = {
+    languages: ['en', 'en-US']
+};
+
+const mockIntlDateTimeFormat = vi.fn(() => ({
+    resolvedOptions: () => ({ timeZone: 'America/New_York' })
+}));
+
+describe('holidayUtils', () => {
+    beforeEach(() => {
+        vi.clearAllMocks();
+        vi.stubGlobal('navigator', mockNavigator);
+        vi.stubGlobal('Intl', {
+            ...Intl,
+            DateTimeFormat: mockIntlDateTimeFormat
+        });
+    });
+
+    describe('getHolidaysForYear', () => {
+        it('should return holidays for a given year and country', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR);
+            expect(holidays).toBeDefined();
+            expect(Array.isArray(holidays)).toBe(true);
+            expect(holidays.length).toBeGreaterThan(0);
+        });
+
+        it('should filter only public holidays', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR);
+            holidays.forEach(holiday => {
+                expect(holiday).toHaveProperty('date');
+                expect(holiday).toHaveProperty('name');
+                expect(holiday.date).toBeInstanceOf(Date);
+                expect(typeof holiday.name).toBe('string');
+            });
+        });
+
+        it('should handle state codes', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR, 'CA');
+            expect(holidays).toBeDefined();
+            expect(Array.isArray(holidays)).toBe(true);
+        });
+
+        it('should return holidays sorted by date', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR);
+            for (let i = 1; i < holidays.length; i++) {
+                const prev = holidays[i - 1].date.getTime();
+                const curr = holidays[i].date.getTime();
+                expect(curr).toBeGreaterThanOrEqual(prev);
+            }
+        });
+
+        it('should handle different countries', () => {
+            const usHolidays = getHolidaysForYear('US', TEST_YEAR);
+            const gbHolidays = getHolidaysForYear('GB', TEST_YEAR);
+            
+            expect(usHolidays.length).toBeGreaterThan(0);
+            expect(gbHolidays.length).toBeGreaterThan(0);
+            expect(usHolidays.length).not.toBe(gbHolidays.length);
+        });
+
+        it('should expand multi-day holidays correctly', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR);
+            const dateKeys = new Set(holidays.map(h => 
+                `${h.date.getFullYear()}-${h.date.getMonth()}-${h.date.getDate()}`
+            ));
+            expect(holidays.length).toBeGreaterThanOrEqual(dateKeys.size);
+        });
+
+        it('should sort holidays by date first, then by name', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR);
+            for (let i = 1; i < holidays.length; i++) {
+                const prev = holidays[i - 1];
+                const curr = holidays[i];
+                const prevTime = prev.date.getTime();
+                const currTime = curr.date.getTime();
+                
+                if (prevTime === currTime) {
+                    expect(curr.name.localeCompare(prev.name)).toBeGreaterThanOrEqual(0);
+                } else {
+                    expect(currTime).toBeGreaterThan(prevTime);
+                }
+            }
+        });
+    });
+
+    describe('optimizeDaysOff', () => {
+        const mockHolidays = [
+            { date: new Date(TEST_YEAR, 0, 1), name: 'New Year' },
+            { date: new Date(TEST_YEAR, 6, 4), name: 'Independence Day' },
+        ];
+
+        describe('basic functionality', () => {
+            it('should return an array of dates', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 5);
+                expect(Array.isArray(result)).toBe(true);
+                result.forEach(date => {
+                    expect(date).toBeInstanceOf(Date);
+                });
+            });
+
+            it('should return at most the requested number of days', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 5);
+                expect(result.length).toBeLessThanOrEqual(5);
+            });
+
+            it('should handle zero days off', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 0);
+                expect(result).toEqual([]);
+            });
+
+            it('should handle more days off than available gaps', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 1000);
+                expect(result.length).toBeGreaterThan(0);
+                expect(result.length).toBeLessThan(1000);
+            });
+        });
+
+        describe('exclusion rules', () => {
+            it('should not include weekends in optimized days', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 10);
+                result.forEach(date => {
+                    expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+
+            it('should not include holidays in optimized days', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 10);
+                const holidayKeys = new Set(mockHolidays.map(h => 
+                    `${h.date.getFullYear()}-${h.date.getMonth()}-${h.date.getDate()}`
+                ));
+                result.forEach(date => {
+                    const dateKey = `${date.getFullYear()}-${date.getMonth()}-${date.getDate()}`;
+                    expect(holidayKeys.has(dateKey)).toBe(false);
+                });
+            });
+
+            it('should not select days that are already holidays or weekends', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Holiday' },
+                    { date: new Date(TEST_YEAR, 0, 3), name: 'Holiday' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 10);
+                const holidaySet = new Set(holidays.map(h => 
+                    `${h.date.getFullYear()}-${h.date.getMonth()}-${h.date.getDate()}`
+                ));
+                result.forEach(date => {
+                    const dateKey = `${date.getFullYear()}-${date.getMonth()}-${date.getDate()}`;
+                    expect(holidaySet.has(dateKey)).toBe(false);
+                    expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+        });
+
+        describe('parameters', () => {
+            it('should respect startDate parameter', () => {
+                const startDate = new Date(TEST_YEAR, 5, 1);
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 5, DEFAULT_WEEKENDS, startDate);
+                result.forEach(date => {
+                    expect(date.getTime()).toBeGreaterThanOrEqual(startDate.getTime());
+                });
+            });
+
+            it('should handle custom weekend days', () => {
+                const result = optimizeDaysOff(mockHolidays, TEST_YEAR, 5, CUSTOM_WEEKENDS);
+                result.forEach(date => {
+                    expect(CUSTOM_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+
+            it('should filter holidays by year and startDate', () => {
+                const holidays = [
+                    { date: new Date(2023, 11, 31), name: 'Old Year' },
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'New Year' },
+                    { date: new Date(TEST_YEAR, 5, 15), name: 'Mid Year' },
+                ];
+                const startDate = new Date(TEST_YEAR, 2, 1);
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 5, DEFAULT_WEEKENDS, startDate);
+                expect(Array.isArray(result)).toBe(true);
+            });
+        });
+
+        describe('gap finding and prioritization', () => {
+            it('should only find gaps of MAX_GAP_LENGTH (5) days or less', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Mon' },
+                    { date: new Date(TEST_YEAR, 0, 3), name: 'Wed' },
+                    { date: new Date(TEST_YEAR, 0, 10), name: 'Wed' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 10);
+                expect(Array.isArray(result)).toBe(true);
+                result.forEach(date => {
+                    expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+
+            it('should find and fill gaps of 1-5 days', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Holiday' },
+                    { date: new Date(TEST_YEAR, 0, 3), name: 'Wed Holiday' },
+                    { date: new Date(TEST_YEAR, 0, 11), name: 'Thu Holiday' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 10);
+                expect(result.length).toBeGreaterThan(0);
+                result.forEach(date => {
+                    expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+
+            it('should prioritize gaps that create longer consecutive periods', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 4), name: 'Thursday Holiday' },
+                    { date: new Date(TEST_YEAR, 0, 8), name: 'Monday Holiday' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 1);
+                expect(result.length).toBe(1);
+            });
+
+            it('should prioritize smaller gaps when they create longer chains', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 4), name: 'Thu Holiday' },
+                    { date: new Date(TEST_YEAR, 0, 9), name: 'Tue Holiday' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 1);
+                expect(result.length).toBe(1);
+                expect(result[0].getDate()).toBe(5);
+            });
+
+            it('should handle multiple gaps and select most efficient ones first', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Mon' },
+                    { date: new Date(TEST_YEAR, 0, 4), name: 'Thu' },
+                    { date: new Date(TEST_YEAR, 0, 8), name: 'Mon' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 3);
+                expect(result.length).toBeLessThanOrEqual(3);
+                result.forEach(date => {
+                    expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+
+            it('should handle backward vs forward chain calculation', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 5), name: 'Friday Holiday' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 1);
+                expect(Array.isArray(result)).toBe(true);
+            });
+
+            it('should optimize to create longer consecutive periods', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 4), name: 'Holiday' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 1);
+                expect(result.length).toBeGreaterThan(0);
+            });
+        });
+
+        describe('edge cases', () => {
+            it('should handle partial gap filling when daysOff is less than gap length', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Mon' },
+                    { date: new Date(TEST_YEAR, 0, 8), name: 'Mon' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 2);
+                expect(result.length).toBe(2);
+                result.forEach(date => {
+                    expect(date.getDate()).toBeGreaterThanOrEqual(2);
+                    expect(date.getDate()).toBeLessThanOrEqual(6);
+                    expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+                });
+            });
+
+            it('should handle multiple gaps when daysOff exceeds single gap capacity', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Mon' },
+                    { date: new Date(TEST_YEAR, 0, 3), name: 'Wed' },
+                    { date: new Date(TEST_YEAR, 0, 5), name: 'Fri' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 3);
+                expect(result.length).toBeGreaterThanOrEqual(2);
+                expect(result.length).toBeLessThanOrEqual(3);
+            });
+
+            it('should handle optimization with no available gaps', () => {
+                const holidays = Array.from({ length: 365 }, (_, i) => {
+                    const date = new Date(TEST_YEAR, 0, 1);
+                    date.setDate(date.getDate() + i);
+                    if (date.getDay() !== 0 && date.getDay() !== 6) {
+                        return { date, name: `Holiday ${i}` };
+                    }
+                    return null;
+                }).filter(Boolean) as Array<{ date: Date; name: string }>;
+                
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+                expect(result).toEqual([]);
+            });
+
+            it('should handle gaps at the start of the year', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 5), name: 'Holiday' },
+                ];
+                const startDate = new Date(TEST_YEAR, 0, 1);
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 5, DEFAULT_WEEKENDS, startDate);
+                expect(Array.isArray(result)).toBe(true);
+            });
+
+            it('should handle gaps at the end of the year', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 11, 25), name: 'Christmas' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+                result.forEach(date => {
+                    expect(date.getFullYear()).toBe(TEST_YEAR);
+                    expect(date.getMonth()).toBeLessThanOrEqual(11);
+                });
+            });
+
+            it('should handle gaps that span year boundaries correctly', () => {
+                const startDate = new Date(TEST_YEAR, 11, 20);
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 11, 25), name: 'Christmas' },
+                ];
+                const result = optimizeDaysOff(holidays, TEST_YEAR, 5, DEFAULT_WEEKENDS, startDate);
+                result.forEach(date => {
+                    expect(date.getFullYear()).toBe(TEST_YEAR);
+                    expect(date.getTime()).toBeGreaterThanOrEqual(startDate.getTime());
+                });
+            });
+        });
+    });
+
+    describe('calculateConsecutiveDaysOff', () => {
+        const mockHolidays = [
+            { date: new Date(TEST_YEAR, 0, 1), name: 'New Year' },
+            { date: new Date(TEST_YEAR, 0, 15), name: 'Holiday' },
+        ];
+
+        describe('basic functionality', () => {
+            it('should return an array of periods', () => {
+                const optimizedDays = [new Date(TEST_YEAR, 0, 2)];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR);
+                expect(Array.isArray(result)).toBe(true);
+            });
+
+            it('should calculate periods with correct structure', () => {
+                const optimizedDays = [new Date(TEST_YEAR, 0, 2)];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR);
+                result.forEach(period => {
+                    expect(period).toHaveProperty('startDate');
+                    expect(period).toHaveProperty('endDate');
+                    expect(period).toHaveProperty('totalDays');
+                    expect(period).toHaveProperty('usedDaysOff');
+                    expect(period.startDate).toBeInstanceOf(Date);
+                    expect(period.endDate).toBeInstanceOf(Date);
+                    expect(typeof period.totalDays).toBe('number');
+                    expect(typeof period.usedDaysOff).toBe('number');
+                });
+            });
+
+            it('should include holidays in consecutive periods', () => {
+                const optimizedDays = [new Date(TEST_YEAR, 0, 2)];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR);
+                const hasPeriodWithHoliday = result.some(period => {
+                    const holidayDate = mockHolidays[0].date;
+                    return period.startDate <= holidayDate && period.endDate >= holidayDate;
+                });
+                expect(hasPeriodWithHoliday).toBe(true);
+            });
+        });
+
+        describe('calculations', () => {
+            it('should calculate totalDays correctly', () => {
+                const optimizedDays = [new Date(TEST_YEAR, 0, 2)];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR);
+                result.forEach(period => {
+                    const calculatedDays = Math.round(
+                        (period.endDate.getTime() - period.startDate.getTime()) / (1000 * 60 * 60 * 24)
+                    ) + 1;
+                    expect(period.totalDays).toBe(calculatedDays);
+                });
+            });
+
+            it('should count usedDaysOff correctly', () => {
+                const optimizedDays = [
+                    new Date(TEST_YEAR, 0, 2),
+                    new Date(TEST_YEAR, 0, 3),
+                ];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR);
+                result.forEach(period => {
+                    expect(period.usedDaysOff).toBeGreaterThanOrEqual(0);
+                    const daysInPeriod = optimizedDays.filter(day => 
+                        day >= period.startDate && day <= period.endDate
+                    ).length;
+                    expect(period.usedDaysOff).toBeLessThanOrEqual(daysInPeriod);
+                });
+            });
+
+            it('should correctly count usedDaysOff in periods', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Holiday' },
+                ];
+                const optimizedDays = [
+                    new Date(TEST_YEAR, 0, 2),
+                    new Date(TEST_YEAR, 0, 3),
+                ];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                const periodWithOptimized = result.find(period =>
+                    optimizedDays.some(day => day >= period.startDate && day <= period.endDate)
+                );
+                if (periodWithOptimized) {
+                    const daysInPeriod = optimizedDays.filter(day =>
+                        day >= periodWithOptimized.startDate && day <= periodWithOptimized.endDate
+                    ).length;
+                    expect(periodWithOptimized.usedDaysOff).toBe(daysInPeriod);
+                }
+            });
+        });
+
+        describe('validation rules', () => {
+            it('should not include periods that are only weekends', () => {
+                const optimizedDays: Date[] = [];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR);
+                result.forEach(period => {
+                    let allWeekends = true;
+                    for (let d = new Date(period.startDate); d <= period.endDate; d.setDate(d.getDate() + 1)) {
+                        const dayOfWeek = d.getDay();
+                        if (dayOfWeek !== 0 && dayOfWeek !== 6) {
+                            allWeekends = false;
+                            break;
+                        }
+                    }
+                    expect(allWeekends).toBe(false);
+                });
+            });
+
+            it('should exclude single-day periods', () => {
+                const holidays: Array<{ date: Date; name: string }> = [];
+                const optimizedDays: Date[] = [];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                result.forEach(period => {
+                    expect(period.totalDays).toBeGreaterThanOrEqual(2);
+                });
+            });
+
+            it('should handle groups that are only weekends correctly', () => {
+                const holidays: Array<{ date: Date; name: string }> = [];
+                const optimizedDays: Date[] = [];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                result.forEach(period => {
+                    let hasNonWeekend = false;
+                    for (let d = new Date(period.startDate); d <= period.endDate; d.setDate(d.getDate() + 1)) {
+                        const dayOfWeek = d.getDay();
+                        if (dayOfWeek !== 0 && dayOfWeek !== 6) {
+                            hasNonWeekend = true;
+                            break;
+                        }
+                    }
+                    expect(hasNonWeekend).toBe(true);
+                });
+            });
+        });
+
+        describe('parameters', () => {
+            it('should respect startDate parameter', () => {
+                const startDate = new Date(TEST_YEAR, 5, 1);
+                const optimizedDays = [new Date(TEST_YEAR, 5, 2)];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR, DEFAULT_WEEKENDS, startDate);
+                result.forEach(period => {
+                    expect(period.startDate.getTime()).toBeGreaterThanOrEqual(startDate.getTime());
+                });
+            });
+
+            it('should handle custom weekend days', () => {
+                const optimizedDays = [new Date(TEST_YEAR, 0, 2)];
+                const result = calculateConsecutiveDaysOff(mockHolidays, optimizedDays, TEST_YEAR, CUSTOM_WEEKENDS);
+                expect(Array.isArray(result)).toBe(true);
+            });
+
+            it('should handle empty optimized days', () => {
+                const result = calculateConsecutiveDaysOff(mockHolidays, [], TEST_YEAR);
+                expect(Array.isArray(result)).toBe(true);
+            });
+        });
+
+        describe('edge cases', () => {
+            it('should handle periods spanning multiple months', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 31), name: 'End of Jan' },
+                ];
+                const optimizedDays = [new Date(TEST_YEAR, 1, 1)];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                expect(Array.isArray(result)).toBe(true);
+            });
+
+            it('should handle periods that start exactly at startDate', () => {
+                const startDate = new Date(TEST_YEAR, 5, 1);
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 5, 1), name: 'Start Holiday' },
+                ];
+                const optimizedDays = [new Date(TEST_YEAR, 5, 3)];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR, DEFAULT_WEEKENDS, startDate);
+                if (result.length > 0) {
+                    expect(result[0].startDate.getTime()).toBeGreaterThanOrEqual(startDate.getTime());
+                }
+            });
+
+            it('should handle periods that end exactly at year end (Dec 31)', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 11, 30), name: 'Dec 30' },
+                ];
+                const optimizedDays = [new Date(TEST_YEAR, 11, 31)];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                const periodAtYearEnd = result.find(period => 
+                    period.endDate.getMonth() === 11 && period.endDate.getDate() === 31
+                );
+                if (periodAtYearEnd) {
+                    expect(periodAtYearEnd.endDate.getFullYear()).toBe(TEST_YEAR);
+                }
+            });
+
+            it('should correctly handle overlapping optimized days and holidays', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Holiday' },
+                ];
+                const optimizedDays = [
+                    new Date(TEST_YEAR, 0, 2),
+                    new Date(TEST_YEAR, 0, 3),
+                ];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                const period = result.find(p => 
+                    p.startDate <= holidays[0].date && p.endDate >= optimizedDays[1]
+                );
+                if (period) {
+                    expect(period.usedDaysOff).toBe(2);
+                }
+            });
+
+            it('should handle consecutive periods separated by work days', () => {
+                const holidays = [
+                    { date: new Date(TEST_YEAR, 0, 1), name: 'Mon' },
+                    { date: new Date(TEST_YEAR, 0, 4), name: 'Thu' },
+                ];
+                const optimizedDays = [
+                    new Date(TEST_YEAR, 0, 2),
+                    new Date(TEST_YEAR, 0, 5),
+                ];
+                const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+                expect(result.length).toBeGreaterThanOrEqual(1);
+                result.forEach(period => {
+                    expect(period.totalDays).toBeGreaterThanOrEqual(2);
+                });
+            });
+        });
+    });
+
+    describe('Integration tests', () => {
+        it('should work together: get holidays, optimize, and calculate periods', () => {
+            const holidays = getHolidaysForYear('US', TEST_YEAR);
+            const optimizedDays = optimizeDaysOff(holidays, TEST_YEAR, 10);
+            const periods = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+
+            expect(holidays.length).toBeGreaterThan(0);
+            expect(optimizedDays.length).toBeLessThanOrEqual(10);
+            expect(Array.isArray(periods)).toBe(true);
+
+            periods.forEach(period => {
+                expect(period.totalDays).toBeGreaterThanOrEqual(2);
+                expect(period.usedDaysOff).toBeGreaterThanOrEqual(0);
+                expect(period.startDate <= period.endDate).toBe(true);
+            });
+        });
+
+        it('should optimize efficiently to maximize consecutive days', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 0, 4), name: 'Holiday' },
+            ];
+            const optimizedDays = optimizeDaysOff(holidays, TEST_YEAR, 1);
+            const periods = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+
+            if (periods.length > 0) {
+                const hasOptimizedDay = periods.some(period =>
+                    optimizedDays.some(day =>
+                        day >= period.startDate && day <= period.endDate
+                    )
+                );
+                expect(hasOptimizedDay).toBe(true);
+            }
+        });
+
+        it('should handle edge case: all days are holidays or weekends', () => {
+            const holidays = Array.from({ length: 50 }, (_, i) => ({
+                date: new Date(TEST_YEAR, 0, i + 1),
+                name: `Holiday ${i + 1}`
+            }));
+            const optimizedDays = optimizeDaysOff(holidays, TEST_YEAR, 5);
+            const periods = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+
+            expect(Array.isArray(optimizedDays)).toBe(true);
+            expect(Array.isArray(periods)).toBe(true);
+        });
+    });
+
+    describe('Edge cases and error handling', () => {
+        it('should handle year with no holidays gracefully', () => {
+            const result = optimizeDaysOff([], TEST_YEAR, 5);
+            expect(Array.isArray(result)).toBe(true);
+        });
+
+        it('should handle invalid country codes gracefully', () => {
+            try {
+                const holidays = getHolidaysForYear('XX', TEST_YEAR);
+                expect(Array.isArray(holidays)).toBe(true);
+            } catch (e) {
+                expect(e).toBeDefined();
+            }
+        });
+
+        it('should handle dates at year boundaries', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 11, 31), name: 'New Year Eve' },
+            ];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+            expect(Array.isArray(result)).toBe(true);
+        });
+
+        it('should handle startDate at end of year', () => {
+            const startDate = new Date(TEST_YEAR, 11, 15);
+            const holidays = [
+                { date: new Date(TEST_YEAR, 11, 25), name: 'Christmas' },
+            ];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 5, DEFAULT_WEEKENDS, startDate);
+            result.forEach(date => {
+                expect(date.getTime()).toBeGreaterThanOrEqual(startDate.getTime());
+                expect(date.getFullYear()).toBe(TEST_YEAR);
+            });
+        });
+
+        it('should handle holidays from previous year correctly', () => {
+            const holidays = [
+                { date: new Date(2023, 11, 31), name: 'Old Year' },
+                { date: new Date(TEST_YEAR, 0, 1), name: 'New Year' },
+            ];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+            expect(Array.isArray(result)).toBe(true);
+        });
+
+        it('should handle leap year correctly', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 1, 29), name: 'Leap Day' },
+            ];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+            expect(Array.isArray(result)).toBe(true);
+        });
+    });
+
+    describe('Private function behavior (tested indirectly)', () => {
+        it('should correctly identify weekend days', () => {
+            const holidays: Array<{ date: Date; name: string }> = [];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 10);
+            result.forEach(date => {
+                expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+            });
+        });
+
+        it('should correctly calculate days between dates', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 0, 1), name: 'Start' },
+            ];
+            const optimizedDays = [new Date(TEST_YEAR, 0, 5)];
+            const result = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+            result.forEach(period => {
+                const calculated = Math.round(
+                    (period.endDate.getTime() - period.startDate.getTime()) / (1000 * 60 * 60 * 24)
+                ) + 1;
+                expect(period.totalDays).toBe(calculated);
+            });
+        });
+
+        it('should generate consistent date keys', () => {
+            const date1 = new Date(TEST_YEAR, 0, 15);
+            const date2 = new Date(TEST_YEAR, 0, 15);
+            const holidays = [
+                { date: date1, name: 'Holiday' },
+            ];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+            const hasDate2 = result.some(d =>
+                d.getFullYear() === date2.getFullYear() &&
+                d.getMonth() === date2.getMonth() &&
+                d.getDate() === date2.getDate()
+            );
+            expect(hasDate2).toBe(false);
+        });
+
+        it('should correctly identify holidays using dateKey', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 0, 15, 10, 30), name: 'Holiday' },
+            ];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 5);
+            const hasHolidayDate = result.some(d =>
+                d.getFullYear() === TEST_YEAR &&
+                d.getMonth() === 0 &&
+                d.getDate() === 15
+            );
+            expect(hasHolidayDate).toBe(false);
+        });
+
+        it('should correctly get weekends for the year with startDate', () => {
+            const startDate = new Date(TEST_YEAR, 5, 1);
+            const holidays: Array<{ date: Date; name: string }> = [];
+            const result = optimizeDaysOff(holidays, TEST_YEAR, 10, DEFAULT_WEEKENDS, startDate);
+            result.forEach(date => {
+                expect(date.getTime()).toBeGreaterThanOrEqual(startDate.getTime());
+                expect(DEFAULT_WEEKENDS).not.toContain(date.getDay());
+            });
+        });
+    });
+
+    describe('Complex scenarios and real-world cases', () => {
+        it('should handle a typical year with multiple holidays and weekends', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 0, 1), name: 'New Year' },
+                { date: new Date(TEST_YEAR, 4, 27), name: 'Memorial Day' },
+                { date: new Date(TEST_YEAR, 6, 4), name: 'Independence Day' },
+                { date: new Date(TEST_YEAR, 8, 2), name: 'Labor Day' },
+                { date: new Date(TEST_YEAR, 10, 28), name: 'Thanksgiving' },
+                { date: new Date(TEST_YEAR, 11, 25), name: 'Christmas' },
+            ];
+            const optimizedDays = optimizeDaysOff(holidays, TEST_YEAR, 10);
+            const periods = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+
+            expect(optimizedDays.length).toBeLessThanOrEqual(10);
+            expect(periods.length).toBeGreaterThan(0);
+            
+            periods.forEach(period => {
+                expect(period.totalDays).toBeGreaterThanOrEqual(2);
+                expect(period.startDate <= period.endDate).toBe(true);
+                expect(period.usedDaysOff).toBeGreaterThanOrEqual(0);
+            });
+        });
+
+        it('should maximize consecutive days off efficiently', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 0, 4), name: 'Thu' },
+                { date: new Date(TEST_YEAR, 0, 8), name: 'Mon' },
+            ];
+            const optimizedDays = optimizeDaysOff(holidays, TEST_YEAR, 1);
+            const periods = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR);
+
+            const periodWithOptimized = periods.find(p =>
+                optimizedDays.some(day => day >= p.startDate && day <= p.endDate)
+            );
+            expect(periodWithOptimized).toBeDefined();
+            if (periodWithOptimized) {
+                expect(periodWithOptimized.totalDays).toBeGreaterThanOrEqual(4);
+            }
+        });
+
+        it('should handle non-standard weekend configurations', () => {
+            const holidays = [
+                { date: new Date(TEST_YEAR, 0, 1), name: 'Holiday' },
+            ];
+            const optimizedDays = optimizeDaysOff(holidays, TEST_YEAR, 5, CUSTOM_WEEKENDS);
+            const periods = calculateConsecutiveDaysOff(holidays, optimizedDays, TEST_YEAR, CUSTOM_WEEKENDS);
+
+            optimizedDays.forEach(date => {
+                expect(CUSTOM_WEEKENDS).not.toContain(date.getDay());
+            });
+
+            expect(Array.isArray(periods)).toBe(true);
+        });
+    });
+});

src/lib/holidayUtils.ts

@@ -31,49 +31,56 @@ export function getHolidaysForYear(countryCode: string, year: number, stateCode?
 }
 
 // Find optimal placement of PTO days to maximize consecutive time off
-export function optimizeDaysOff(holidays: { date: Date }[], year: number, daysOff: number, weekendDays: number[] = [0, 6]): Date[] {
+export function optimizeDaysOff(holidays: { date: Date }[], year: number, daysOff: number, weekendDays: number[] = [0, 6], startDate?: Date): Date[] {
+    const effectiveStartDate = startDate || new Date(year, 0, 1);
+    const filteredHolidays = holidays.filter(h => h.date.getFullYear() === year && h.date >= effectiveStartDate);
     const allDaysOff = new Set([
-        ...holidays.filter(h => h.date.getFullYear() === year).map(h => dateKey(h.date)),
-        ...getWeekends(year, weekendDays).map(d => dateKey(d))
+        ...filteredHolidays.map(h => dateKey(h.date)),
+        ...getWeekends(year, weekendDays, effectiveStartDate).map(d => dateKey(d))
     ]);
 
-    const gaps = findGaps(allDaysOff, year, weekendDays);
+    const gaps = findGaps(allDaysOff, year, weekendDays, effectiveStartDate);
     return selectDaysOff(rankGapsByEfficiency(gaps, allDaysOff, weekendDays), daysOff, allDaysOff, weekendDays);
 }
 
 // Calculate periods of consecutive days off (weekends + holidays + PTO)
-export function calculateConsecutiveDaysOff(holidays: { date: Date }[], optimizedDaysOff: Date[], year: number, weekendDays: number[] = [0, 6]) {
+export function calculateConsecutiveDaysOff(holidays: { date: Date }[], optimizedDaysOff: Date[], year: number, weekendDays: number[] = [0, 6], startDate?: Date) {
+    const effectiveStartDate = startDate || new Date(year, 0, 1);
+    const filteredHolidays = holidays.filter(h => h.date >= effectiveStartDate);
+    const filteredOptimizedDaysOff = optimizedDaysOff.filter(d => d >= effectiveStartDate);
+    
     const allDaysOff = new Set([
-        ...holidays.map(h => dateKey(h.date)),
-        ...optimizedDaysOff.map(d => dateKey(d)),
-        ...getWeekends(year, weekendDays).map(d => dateKey(d))
+        ...filteredHolidays.map(h => dateKey(h.date)),
+        ...filteredOptimizedDaysOff.map(d => dateKey(d)),
+        ...getWeekends(year, weekendDays, effectiveStartDate).map(d => dateKey(d))
     ]);
 
     const consecutiveDaysOff = [];
     let currentGroup = [];
 
-    for (let d = new Date(year, 0, 1); d <= new Date(year, 11, 31); d.setDate(d.getDate() + 1)) {
-        if (isWeekend(d, weekendDays) || isHoliday(d, holidays) || allDaysOff.has(dateKey(d))) {
+    for (let d = new Date(effectiveStartDate); d <= new Date(year, 11, 31); d.setDate(d.getDate() + 1)) {
+        if (isWeekend(d, weekendDays) || isHoliday(d, filteredHolidays) || allDaysOff.has(dateKey(d))) {
             currentGroup.push(new Date(d));
         } else if (currentGroup.length > 0) {
             if (isValidConsecutiveGroup(currentGroup, weekendDays)) {
-                consecutiveDaysOff.push(createPeriod(currentGroup, optimizedDaysOff));
+                consecutiveDaysOff.push(createPeriod(currentGroup, filteredOptimizedDaysOff));
             }
             currentGroup = [];
         }
     }
 
     if (currentGroup.length > 0 && isValidConsecutiveGroup(currentGroup, weekendDays)) {
-        consecutiveDaysOff.push(createPeriod(currentGroup, optimizedDaysOff));
+        consecutiveDaysOff.push(createPeriod(currentGroup, filteredOptimizedDaysOff));
     }
 
     return consecutiveDaysOff;
 }
 
 // Get all weekend days for a year
-function getWeekends(year: number, weekendDays: number[]): Date[] {
+function getWeekends(year: number, weekendDays: number[], startDate?: Date): Date[] {
+    const effectiveStartDate = startDate || new Date(year, 0, 1);
     const weekends = [];
-    for (let d = new Date(year, 0, 1); d <= new Date(year, 11, 31); d.setDate(d.getDate() + 1)) {
+    for (let d = new Date(effectiveStartDate); d <= new Date(year, 11, 31); d.setDate(d.getDate() + 1)) {
         if (d.getMonth() === d.getMonth() && isWeekend(d, weekendDays)) {
             weekends.push(new Date(d));
         }
@@ -82,11 +89,12 @@ function getWeekends(year: number, weekendDays: number[]): Date[] {
 }
 
 // Find gaps between days off that could be filled with PTO
-function findGaps(allDaysOff: Set<string>, year: number, weekendDays: number[]) {
+function findGaps(allDaysOff: Set<string>, year: number, weekendDays: number[], startDate?: Date) {
+    const effectiveStartDate = startDate || new Date(year, 0, 1);
     const gaps = [];
     let gapStart = null;
 
-    for (let d = new Date(year, 0, 1); d <= new Date(year, 11, 31); d.setDate(d.getDate() + 1)) {
+    for (let d = new Date(effectiveStartDate); d <= new Date(year, 11, 31); d.setDate(d.getDate() + 1)) {
         if (!allDaysOff.has(dateKey(d)) && !isWeekend(d, weekendDays)) {
             if (!gapStart) gapStart = new Date(d);
         } else if (gapStart) {

src/routes/+page.svelte

@@ -17,6 +17,8 @@
     let daysOff: number = 0;
     let optimizedDaysOff: Date[] = [];
     let consecutiveDaysOff: Array<{ startDate: Date; endDate: Date; totalDays: number }> = [];
+    let showExcludedMonths: boolean = true;
+    let visibleMonths: number[] = [];
     let countriesInput: HTMLInputElement | null = null;
     let statesInput: HTMLInputElement | null = null;
     let showHowItWorks: boolean = false;
@@ -35,12 +37,27 @@
     let showWeekendSettings: boolean = false;
     let weekendDays: number[] = [];
 
+    // Start date state
+    let startDate: Date = new Date(new Date().getFullYear(), 0, 1);
+    let showDatePicker: boolean = false;
+    let datePickerValue: string = '';
+
     $: selectedCountryCode = Object.keys(countriesList).find(code => countriesList[code] === selectedCountry) || '';
 
-    $: if (selectedCountryCode || selectedStateCode || daysOff || year) {
+    $: if (selectedCountryCode || selectedStateCode || daysOff || year || startDate) {
         updateHolidays();
     }
 
+    // Reactive: when year changes, load start date for that year
+    $: if (year !== undefined && year) {
+        startDate = getStartDate(year);
+    }
+    
+    // Reactive: when startDate or year changes, update excluded months visibility
+    $: if (year !== undefined && year && startDate) {
+        showExcludedMonths = !hasExcludedMonths();
+    }
+
     $: if (daysOff) {
         localStorage.setItem('daysOff', daysOff.toString());
     }
@@ -59,8 +76,11 @@
         const stateName = target.value;
         selectedStateCode = Object.keys(statesList).find(code => statesList[code] === stateName) || '';
         selectedState = stateName;
-        localStorage.setItem('selectedState', selectedState);
-        localStorage.setItem('selectedStateCode', selectedStateCode);
+        // Save state per country
+        if (selectedCountryCode) {
+            localStorage.setItem(`selectedState_${selectedCountryCode}`, selectedState);
+            localStorage.setItem(`selectedStateCode_${selectedCountryCode}`, selectedStateCode);
+        }
     }
 
     onMount(() => {
@@ -73,14 +93,22 @@
             const storedYear = localStorage.getItem('year');
             const storedCountry = localStorage.getItem('selectedCountry');
             const storedDaysOff = localStorage.getItem('daysOff');
-            const storedState = localStorage.getItem('selectedState');
-            const storedStateCode = localStorage.getItem('selectedStateCode');
 
             year = storedYear ? parseInt(storedYear, 10) : defaultYear;
             selectedCountry = storedCountry || defaultCountry;
             daysOff = storedDaysOff ? parseInt(storedDaysOff, 10) : defaultDaysOff;
-            selectedState = storedState || '';
-            selectedStateCode = storedStateCode || '';
+            
+            // Load state per country
+            const countryCode = Object.keys(countriesList).find(code => countriesList[code] === selectedCountry) || '';
+            if (countryCode) {
+                selectedState = localStorage.getItem(`selectedState_${countryCode}`) || '';
+                selectedStateCode = localStorage.getItem(`selectedStateCode_${countryCode}`) || '';
+            } else {
+                selectedState = '';
+                selectedStateCode = '';
+            }
+            startDate = getStartDate(year);
+            // showExcludedMonths will be set by reactive statement
             updateHolidays();
         });
 
@@ -113,14 +141,17 @@
     function handleCountryChange(event: Event) {
         const target = event.target as HTMLInputElement;
         const fullValue = target.value;
-        if (selectedCountryCode) {
-            daysOff = ptoData[selectedCountryCode] || 0;
-            selectedState = ''; // Reset state
-            selectedStateCode = ''; // Reset state code
-            updateStatesList(selectedCountryCode); // Update states list for the new country
+        selectedCountry = fullValue;
+        // Get the country code for the new country (selectedCountryCode will update reactively)
+        const newCountryCode = Object.keys(countriesList).find(code => countriesList[code] === fullValue) || '';
+        if (newCountryCode) {
+            // Update days off to the new country's default
+            daysOff = ptoData[newCountryCode] || 0;
+            // Load state for the new country
+            selectedState = localStorage.getItem(`selectedState_${newCountryCode}`) || '';
+            selectedStateCode = localStorage.getItem(`selectedStateCode_${newCountryCode}`) || '';
+            // updateStatesList and updateHolidays will be called by reactive statements
             localStorage.setItem('selectedCountry', selectedCountry);
-            localStorage.setItem('selectedState', selectedState);
-            localStorage.setItem('selectedStateCode', selectedStateCode);
             localStorage.setItem('daysOff', daysOff.toString());
         }
     }
@@ -135,8 +166,8 @@
                 hidden: isHolidayHidden(holiday)
             }));
             const visibleHolidays = holidays.filter(h => !h.hidden);
-            optimizedDaysOff = optimizeDaysOff(visibleHolidays, year, daysOff, weekendDays);
-            consecutiveDaysOff = calculateConsecutiveDaysOff(visibleHolidays, optimizedDaysOff, year, weekendDays);
+            optimizedDaysOff = optimizeDaysOff(visibleHolidays, year, daysOff, weekendDays, startDate);
+            consecutiveDaysOff = calculateConsecutiveDaysOff(visibleHolidays, optimizedDaysOff, year, weekendDays, startDate);
         } else {
             holidays = [];
             optimizedDaysOff = [];
@@ -147,14 +178,18 @@
     function resetToDefault() {
         year = defaultYear;
         selectedCountry = defaultCountry;
-        selectedState = '';
-        selectedStateCode = '';
-        daysOff = defaultDaysOff;
+        const defaultCountryCode = Object.keys(countriesList).find(code => countriesList[code] === defaultCountry) || '';
+        // Load state for default country
+        if (defaultCountryCode) {
+            selectedState = localStorage.getItem(`selectedState_${defaultCountryCode}`) || '';
+            selectedStateCode = localStorage.getItem(`selectedStateCode_${defaultCountryCode}`) || '';
+        } else {
+            selectedState = '';
+            selectedStateCode = '';
+        }
+        // Keep current daysOff value, don't reset it
         localStorage.setItem('year', year.toString());
         localStorage.setItem('selectedCountry', selectedCountry);
-        localStorage.setItem('selectedState', selectedState);
-        localStorage.setItem('selectedStateCode', selectedStateCode);
-        localStorage.setItem('daysOff', daysOff.toString());
     }
 
     function handleKeyDown(event: KeyboardEvent) {
@@ -252,6 +287,156 @@
 
     $: visibleHolidaysCount = holidays.filter(h => !h.hidden).length;
 
+    // Get start date for a given year from localStorage
+    function getStartDate(year: number): Date {
+        try {
+            const stored = localStorage.getItem('startDates');
+            if (stored) {
+                const startDates: string[] = JSON.parse(stored);
+                // Find date that matches the year (extract year from date string)
+                const dateStr = startDates.find(date => {
+                    const dateYear = parseInt(date.split('-')[0] || date.split('T')[0].split('-')[0]);
+                    return dateYear === year;
+                });
+                if (dateStr) {
+                    // Parse date string - handle both YYYY-MM-DD and ISO format
+                    const parsed = dateStr.includes('T') ? dateStr.split('T')[0] : dateStr;
+                    const [y, m, d] = parsed.split('-').map(Number);
+                    return new Date(y, m - 1, d);
+                }
+            }
+        } catch (e) {
+            console.error('Error loading start date:', e);
+        }
+        return new Date(year, 0, 1); // Default to Jan 1st
+    }
+
+    // Save start date for a given year to localStorage
+    function saveStartDate(year: number, date: Date) {
+        try {
+            const stored = localStorage.getItem('startDates');
+            let startDates: string[] = stored ? JSON.parse(stored) : [];
+            // Remove existing date for this year (extract year from date string)
+            startDates = startDates.filter(dateStr => {
+                const dateYear = parseInt(dateStr.split('-')[0] || dateStr.split('T')[0].split('-')[0]);
+                return dateYear !== year;
+            });
+            // Add new date
+            startDates.push(formatDateForInput(date));
+            localStorage.setItem('startDates', JSON.stringify(startDates));
+        } catch (e) {
+            console.error('Error saving start date:', e);
+        }
+    }
+
+    // Format date as YYYY-MM-DD for date input (no timezone conversion)
+    function formatDateForInput(date: Date): string {
+        const year = date.getFullYear();
+        const month = String(date.getMonth() + 1).padStart(2, '0');
+        const day = String(date.getDate()).padStart(2, '0');
+        return `${year}-${month}-${day}`;
+    }
+
+    // Format start date for display
+    function formatStartDate(date: Date): string {
+        const today = new Date();
+        if (date.getTime() === new Date(today.getFullYear(), today.getMonth(), today.getDate()).getTime() && date.getFullYear() === year) {
+            return 'Today';
+        }
+        const monthNames = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
+        const day = date.getDate();
+        const suffix = getDaySuffix(day);
+        return `${monthNames[date.getMonth()]}&nbsp;${day}${suffix}`;
+    }
+
+    // Get day suffix (st, nd, rd, th)
+    function getDaySuffix(day: number): string {
+        if (day > 3 && day < 21) return 'th';
+        switch (day % 10) {
+            case 1: return 'st';
+            case 2: return 'nd';
+            case 3: return 'rd';
+            default: return 'th';
+        }
+    }
+
+    // Handle start date change
+    function handleStartDateChange(newDate: Date) {
+        startDate = newDate;
+        saveStartDate(year, newDate);
+        updateHolidays();
+        // showExcludedMonths will be updated by reactive statement
+    }
+
+    // Handle date picker input change (auto-save)
+    function handleDatePickerChange() {
+        if (datePickerValue) {
+            // Parse YYYY-MM-DD format in local time (consistent with getStartDate)
+            const [y, m, d] = datePickerValue.split('-').map(Number);
+            const newDate = new Date(y, m - 1, d);
+            handleStartDateChange(newDate);
+        }
+    }
+
+    // Set start date to today
+    function setStartDateToToday() {
+        const today = new Date();
+        if (today.getFullYear() === year) {
+            handleStartDateChange(new Date(today.getFullYear(), today.getMonth(), today.getDate()));
+            showDatePicker = false;
+        }
+    }
+
+    // Reset start date to Jan 1st
+    function resetStartDateToJan1() {
+        const jan1st = new Date(year, 0, 1);
+        handleStartDateChange(jan1st);
+        showDatePicker = false;
+    }
+
+    // Check if today is in the current year
+    function isTodayInYear(): boolean {
+        const today = new Date();
+        return today.getFullYear() === year;
+    }
+
+    // Helper: Get start date normalized to the current year
+    function getStartDateInYear(): Date {
+        return new Date(year, startDate.getMonth(), startDate.getDate());
+    }
+
+    // Check if a month is active (not entirely before the start date)
+    function isMonthActive(monthIndex: number): boolean {
+        const startDateInYear = getStartDateInYear();
+        const startMonth = startDateInYear.getMonth();
+        
+        // Month is active if:
+        // 1. The start date falls within this month (same month), OR
+        // 2. The month starts on or after the start date (later month)
+        // This means only months entirely before the start date's month are excluded
+        return monthIndex >= startMonth;
+    }
+
+    // Check if start date is Jan 1st
+    function isStartDateJan1st(): boolean {
+        const startDateInYear = getStartDateInYear();
+        return startDateInYear.getTime() === new Date(year, 0, 1).getTime();
+    }
+
+    // Check if there are any excluded months (months entirely before the start date)
+    function hasExcludedMonths(): boolean {
+        return months.some(month => !isMonthActive(month));
+    }
+
+    // Filter months based on showExcludedMonths setting
+    // Explicitly depend on startDate, year, and showExcludedMonths to ensure proper reactivity
+    // Use a computed value that depends on all relevant variables
+    $: visibleMonths = (startDate && year !== undefined && year) 
+        ? (showExcludedMonths 
+            ? months 
+            : months.filter(month => isMonthActive(month)))
+        : [];
+
     function toggleWeekendDay(dayNumber: number) {
         if (weekendDays.includes(dayNumber)) {
             weekendDays = weekendDays.filter(d => d !== dayNumber);
@@ -318,7 +503,7 @@
 
     .content-box p {
         text-align: center;
-        line-height: 2;
+        line-height: 3;
     }
 
     input {
@@ -365,6 +550,29 @@
         }
     }
 
+    .toggle-excluded-months-container {
+        text-align: center;
+        margin: 20px 0;
+    }
+
+    .toggle-excluded-months {
+        padding: 8px 16px;
+        background-color: #333;
+        border: 1px solid #555;
+        border-radius: 5px;
+        color: #fff;
+        cursor: pointer;
+        font-size: 0.9em;
+        transition: background-color 0.3s;
+        width: auto;
+        display: inline-block;
+        white-space: nowrap;
+    }
+
+    .toggle-excluded-months:hover {
+        background-color: #444;
+    }
+
     .calendar-container {
         width: 100%;
         max-width: 300px;
@@ -557,7 +765,6 @@
     }
 
     .content-box button {
-        margin-left: 10px;
         background-color: #444;
         border: none;
         color: #fff;
@@ -641,6 +848,161 @@
         margin-bottom: 15px;
         color: #fff;
     }
+
+    .start-date-link {
+        text-decoration: underline;
+        text-decoration-style: dotted;
+        cursor: pointer;
+        color: inherit;
+    }
+
+    .start-date-link:hover {
+        text-decoration-style: solid;
+    }
+
+    .date-picker-overlay {
+        position: fixed;
+        top: 0;
+        left: 0;
+        width: 100%;
+        height: 100%;
+        background-color: rgba(0, 0, 0, 0.7);
+        display: flex;
+        justify-content: center;
+        align-items: center;
+        z-index: 1000;
+    }
+
+    .date-picker-modal {
+        background-color: #222;
+        border-radius: 10px;
+        padding: 25px;
+        max-width: min(400px, calc(100vw - 40px));
+        width: 100%;
+        box-sizing: border-box;
+        position: relative;
+        color: #fff;
+    }
+
+    .date-picker-close {
+        position: absolute;
+        top: 10px;
+        right: 10px;
+        background: transparent;
+        border: none;
+        color: #fff;
+        font-size: 24px;
+        cursor: pointer;
+        width: 30px;
+        height: 30px;
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        padding: 0;
+        line-height: 1;
+    }
+
+    .date-picker-close:hover,
+    .date-picker-close:active,
+    .date-picker-close:focus {
+        background: transparent;
+        color: #ccc;
+    }
+
+    .date-picker-modal h3 {
+        margin: 0 0 10px 0;
+        padding: 0;
+        text-align: center;
+        font-size: 1.5em;
+    }
+
+    .date-picker-modal p {
+        margin: 0 0 20px 0;
+        padding: 0;
+        text-align: center;
+        color: #ccc;
+    }
+
+    .date-picker-controls {
+        margin: 0 0 20px 0;
+        padding: 0;
+        width: 100%;
+    }
+
+    .date-input {
+        width: 100%;
+        padding: 10px;
+        font-size: 1em;
+        background-color: #222;
+        border: 1px solid #555;
+        border-radius: 5px;
+        color: #fff;
+        box-sizing: border-box;
+        text-align: center;
+        margin: 0;
+        display: block;
+    }
+
+    .date-input:focus {
+        outline: 2px solid #61dafb;
+        border-color: #61dafb;
+    }
+
+    /* Make calendar icon white */
+    .date-input::-webkit-calendar-picker-indicator {
+        filter: invert(1);
+        cursor: pointer;
+    }
+
+    .date-input::-webkit-inner-spin-button,
+    .date-input::-webkit-clear-button {
+        filter: invert(1);
+    }
+
+    .date-picker-buttons {
+        display: flex;
+        gap: 10px;
+        justify-content: center;
+        margin: 0 0 15px 0;
+        width: 100%;
+        box-sizing: border-box;
+    }
+
+    .date-picker-button,
+    .date-picker-save {
+        margin: 0;
+        border: none;
+        border-radius: 5px;
+        cursor: pointer;
+        transition: background-color 0.3s;
+        box-sizing: border-box;
+    }
+
+    .date-picker-button {
+        flex: 1;
+        min-width: 0;
+        padding: 20px;
+        background-color: #444;
+        color: #fff;
+        font-size: 0.9em;
+    }
+
+    .date-picker-button:hover {
+        background-color: #555;
+    }
+
+    .date-picker-save {
+        width: 100%;
+        margin: 0;
+        font-size: 1.1em;
+        font-weight: bold;
+        background-color: #61dafb;
+        color: #000;
+    }
+
+    .date-picker-save:hover {
+        background-color: #4fa8c5;
+    }
 </style>
 
 <main>
@@ -689,15 +1051,27 @@
                 <span class="bold">{daysOff}</span>
                 <button on:click={() => { daysOff++; updateHolidays(); }} aria-label="Increase days off">▲</button>
             </span>
-            days&nbsp;off in
+            days&nbsp;off from
+            <a href="#" on:click|preventDefault={() => { showDatePicker = true; datePickerValue = formatDateForInput(startDate); }} class="bold start-date-link">
+                {@html formatStartDate(startDate)}
+            </a>
+            until the&nbsp;end&nbsp;of
             <span class="arrow-controls">
                 <button on:click={() => { year--; updateHolidays(); }} aria-label="Previous year">◀</button>
                 <span class="bold">{year}</span>
                 <button on:click={() => { year++; updateHolidays(); }} aria-label="Next year">▶</button>
             </span>
         </p>
-        {#if year !== defaultYear || selectedCountry !== defaultCountry || daysOff !== defaultDaysOff}
-            <a href="#" on:click|preventDefault={resetToDefault} class="reset-link">Reset to my country</a>
+        {#if year !== defaultYear || selectedCountry !== defaultCountry}
+            {@const yearDifferent = year !== defaultYear}
+            {@const countryDifferent = selectedCountry !== defaultCountry}
+            <a href="#" on:click|preventDefault={resetToDefault} class="reset-link">
+                {yearDifferent && countryDifferent 
+                    ? 'Reset to current country and year'
+                    : yearDifferent 
+                    ? 'Reset to current year'
+                    : 'Reset to current country'}
+            </a>
         {/if}
 
         <datalist id="countries">
@@ -781,13 +1155,27 @@
         </div>
         {/if}
 
+        {#if hasExcludedMonths()}
+        <div class="toggle-excluded-months-container">
+            <button 
+                class="toggle-excluded-months" 
+                on:click={() => showExcludedMonths = !showExcludedMonths}
+                aria-label={showExcludedMonths ? 'Hide excluded months' : 'Show excluded months'}
+            >
+                {showExcludedMonths ? 'Hide' : 'Show'} excluded months
+            </button>
+        </div>
+        {/if}
+
         <div class="calendar-grid">
-            {#each months as month}
+            {#each visibleMonths as month}
                 <div class="calendar-container">
                     <CalendarMonth
                         year={year}
                         month={month}
                         holidays={holidays}
+                        startDate={startDate}
+                        isActive={isMonthActive(month)}
                         optimizedDaysOff={optimizedDaysOff}
                         consecutiveDaysOff={consecutiveDaysOff}
                         selectedCountryCode={selectedCountryCode}
@@ -798,6 +1186,41 @@
         </div>
     </div>
 
+    {#if showDatePicker}
+    <div class="date-picker-overlay" on:click|self={() => showDatePicker = false}>
+        <div class="date-picker-modal" on:click|stopPropagation>
+            <button class="date-picker-close" on:click={() => showDatePicker = false} aria-label="Close">×</button>
+            <h3>Set Start Date</h3>
+            <p>Choose when your time off period begins for {year}</p>
+            <div class="date-picker-controls">
+                <input 
+                    type="date" 
+                    bind:value={datePickerValue}
+                    on:change={handleDatePickerChange}
+                    class="date-input"
+                    min={formatDateForInput(new Date(year, 0, 1))}
+                    max={formatDateForInput(new Date(year, 11, 31))}
+                />
+            </div>
+            <div class="date-picker-buttons">
+                {#if isTodayInYear()}
+                    <button on:click={setStartDateToToday} class="date-picker-button">
+                        Set to today
+                    </button>
+                {/if}
+                {#if !isStartDateJan1st()}
+                    <button on:click={resetStartDateToJan1} class="date-picker-button">
+                        Reset to Jan 1st
+                    </button>
+                {/if}
+            </div>
+            <button class="date-picker-button date-picker-save" on:click={() => showDatePicker = false}>
+                Done
+            </button>
+        </div>
+    </div>
+    {/if}
+
     <button type="button" class="toggle-text" on:click={toggleHowItWorks}>
         {showHowItWorks ? 'Hide Details' : 'How does this work?'}
     </button>

vite.config.ts

@@ -2,5 +2,10 @@ import { sveltekit } from '@sveltejs/kit/vite';
 import { defineConfig } from 'vite';
 
 export default defineConfig({
-	plugins: [sveltekit()]
+	plugins: [sveltekit()],
+	test: {
+		globals: true,
+		environment: 'node',
+		include: ['src/**/*.{test,spec}.{js,ts}']
+	}
 });