Fix off-by-one calendar months with time zones that are greater than UTC+0 (GMT+0).
Fix https://github.com/matrix-org/matrix-public-archive/issues/77
Previously, we would calculate `lastDayOfTheMonthDate` in the local timezone because we were using the vanilla `new Date(year, month, 0)` constructor. For any timezone greater than `UTC+0` (like London UTC+1 or Korea UTC +9), this means that the date is a day-behind when we go back to UTC+0.
**Before:**
```
inputDate Fri, 29 Jul 2022 00:00:00 GMT 1659052800000
lastDayOfTheMonthDate Sat, 30 Jul 2022 23:00:00 GMT 1659222000000
lastDayOfTheMonth 30
```
**After**
```
inputDate Fri, 29 Jul 2022 00:00:00 GMT 1659052800000
lastDayOfTheMonthDate Sun, 31 Jul 2022 00:00:00 GMT 1659225600000
lastDayOfTheMonth 31
```
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