3d89eb8582
Some countries (e.g. Russia, or Vietnam) have holidays which span several days. Rather than using `holiday.date` from the date-holidays library, we can check the `.start` (inclusive) and `.end` (exclusive) dates, and use these to show multiple holiday days on the calendar. However since these properties return a `Date` representing the start of the day in that country, rather than an ISO string like `.date` does, we also need to pass in the current browser `timezone` to the library, so that we show the correct dates to the user.