fix: Use refined dayjs parsing in date/time inputs

[distantnative]

Review

• Design & concept
• Rough pass
• Manual testing

Timing: no rush

Description

Wrap-up of the dayjs work: this connects k-date-input/k-time-input to the new dayjs.parse() and fixes the input behavior that the old interpret() call could never get right. The inputs now read what you typed against the field's own display pattern.

Changelog

✨ Enhancements

• Date and time fields show an example of their display format as placeholder, so the expected notation is visible before typing.
  https://feedback.getkirby.com/746
• The display format of date and time fields supports escaped literals, e.g. HH[h]mm or D [de] MMMM YYYY

🐛 Bug fixes

• Date and time fields read your input in the field's own display format instead of guessing
  Date/time field: unexpected results for arbitrary formats #6309
  Date field value resets when pressing "save". #8024
  [Panel] - Bug with date field when included in a structure field #6282
  Date fields behave erratically when entering dates in M/D/YY format. #4211
  Date field behaves weird when "display" MM/YYYY is used #6408
  Date in structure field doesn't work when using the display tag to change the order of YYYY-MM-DD #7342
• Input that cannot be read is kept and the field marked invalid, instead of silently clearing the field
• Time fields word their min/max validation messages as times instead of dates

Docs

display option (date, datetime, time fields)

Anything dayjs formats works, and
text you want printed as it is goes in square brackets:

fields:
  meeting:
    type: date
    display: D. MMMM YYYY
    time:
      display: HH[h]mm

For review team

• Add lab and/or sandbox examples (wherever helpful)
  • New date and time field examples on sandbox repo
  • https://sandbox.test/panel/lab/internals/library.dayjs/1_dayjs and all tabs
• Add changes & docs to release notes draft in Notion

[bastianallgeier]

It all works great and I love the placeholders. But there's a small tabbing bug, when I tab into the field with the custom strings …

CleanShot.2026-08-15.at.12.20.20.mp4

[distantnative]

@bastianallgeier improved/fixed that behavior (and related general tab key behavior)

[bastianallgeier]

It works great now and it's pretty mindblowing how great the usabilty of all of this now is 💛

One more thing. I've seen this example in the display tab, but it does not really change width at all. What is this supposed to do? Should the entire field width change or do I misunderstand it?

[distantnative]

Variable width here refers to the width of the month names. The display token is three characters wide but the actual display can vary in its length. I understand that it's confusing with not referring to the field width.

[bastianallgeier]

Ahh, that makes total sense. Maybe we should rename the label to "Variable month name width". That also works like a charm btw. I would say that this PR is ready from what I've tested.