UI Fix for backfill date picker

[Tomi-1997]

Fixes Backfill date picker randomly changing the date when it is full and then modified.

Closes: #57544

Problem

• Fill a date picker form, then modify the year.
• Any subsequent change will increase the other fields (days, or seconds)
  

Solution

• Change the parsing process from
  Create day.js from date string
  Convert with timezone to another day.js
• To
  Create day.js using date string and a timezone
  

I think consecutive conversions causes an offset to be added, but this seems to fix it.
This keeps the same behavior as before (value as utc, display value as local time)

[pierrejeambrun]

Thanks your for the PR.

I tried your change locally and the issue seems to persist for years on my end. Are you using a specific browser for this to work?

I have attached a video. When I edit the time, day or month, everything is fine, when I edit the year, (I tried to input 2024), it resets to 1902then 1900, then 1902, then 1904. (only the last digit is taken into account). Same if I hit delete year before trying a new input value.

Screen.Recording.2025-11-07.at.16.49.15.mov

[Tomi-1997]

Hi! This is mainly to fix a bug which is related to the issue you are describing.

When the date is filled, and you try to modify the year, it applies only 1 digit, like you've said, and resets to 1900 or 1901.
Then every subsequent key type, on any field, causes other fields to change.
(On chrome and edge, but can also be produced on fire fox)

Using firefox, it seems the default date picked is used, and modifying the year functions as intended.
However, I still managed to produce the bug:

[pierrejeambrun]

@Tomi-1997 Thanks for your reply.

I understand that this pull request is fixing the 'other fields' flickering, but the 'year' field remain bugged as mentionned above. Is that outside the scope of this PR and should be treated separately or is this PR supposed to also address that ?

Maybe we can go ahead and merge this fix and follow up with another PR to fix specifically the year field?

mistake

[Tomi-1997]

@pierrejeambrun
Hi
The 'year' bug is outside the scope of this PR, I also believe it should be addressed in a different PR

[pierrejeambrun]

Nice. Weird there is not the CI backport automatic message, as if the backport was not done.