Weekday changes with the machine timezone

[m-anwr]

To Reproduce
Steps to reproduce the behavior:

1. Go to your OS settings
2. Change timezone to UTC
3. Open the datepicker on December 1st, 2025
4. See December 1st as a Monday
5. Go to your OS settings
6. Change timezone to far west in the US like Alaska
7. Open the datepicker on December 1st, 2025
8. See December 1st as a Sunday

Expected behavior
December 1st, 2025 should always be the same no matter what the timezone is (in this case it's a Monday)

Screenshots
with UTC as timezone for the OS:

With Alaska as timezone for the OS:

[kouts]

Adding a bit more detail: the underlying date value is always correct, the issue seems to be only with how the calendar grid is rendered. December 1st, 2025 is a Monday in every timezone, so seeing it shift to Sunday means the month matrix is being generated using a timezone-dependent Date(?).

Timezone should affect the time, not which weekday a calendar date falls on. This is why the datepicker shows the correct value, but the grid alignment is wrong.

[kouts]

Thanks for the fix @Jasenkoo

[ChronosMasterOfAllTime]

@Jasenkoo I added a PR as an addendum to this. See #1199