Date fields with 12 hour time flip-flopping between AM/PM on change

[simonworkhouse]

Bug description

The day period (AM/PM) changes on update for date fields displayed in a locale with a 12 hour time format which also have a display timezone set that is different to the browser's default timezone.

This is related to the previous issue #14249 which was addressed by updating reka-ui in the PR #14259. I have a very basic example test and a potential fix implemented but will probably not be able to report the bug until next week unovue/reka-ui@v2...simonworkhouse:reka-ui:bugfix/day-period-incorrectly-handled

Screencast.from.2026-09-18.17-19-45.webm

How to reproduce

Create a date field with time that displays time in a timezone offset to yours and change the hour input until the bug triggers.

Logs

Environment

N/A

Installation

Fresh statamic/statamic site via CLI

Additional details

No response

[duncanmcclean]

Can you provide the full output of php please support:details?