Property Editors: DateTimeWithTimeZone - Changing timezone mode to Local shows invalid time zone error

[lauraneto]

Changes

• Adjusted the Umbraco.DateTimeWithTimeZone editor to, when in Local mode, store the date as UTC in the database. This makes it so the stored data is consistent and does not vary depending on the time zone of the user viewing it.
• Now not validating the "selected time zone" when mode is Local, as that will always be stored in UTC and not from a list.
• Now checking if the expected value matches the stored value when loading the property, to trigger a change if needed to ensure the stored value is consistent. (this can happen if you change between editors, where a time zone was stored but is not relevant anymore, or if you switch from a All or Custom to Local, where the date should be stored in UTC)
• Adjusted the value converter mappings to truncate the datetime whenever the editor was switched from one with more information to less (e.g. Date Time with Time Zone to Date Time Unspecified, 2025-10-10T00:00:00+02:00 -> 2025-10-10T00:00:00), as it was already the case when returning the date to the client.

Testing
For testing the initial reported issue, in which a validation error was shown when switching between All or Custom to Local and trying to publish the page:

1. Create a document with a Date Time with Time Zone picker.
2. Configure the picker to allow all time zones.
3. Go to the document and select a date and a random time zone (that not your local) and publish the page.
4. Go to the date time data type and change the Time zones to Local.
5. Go back to the document and try to publish it.

I did end up fixing some other inconsistencies when changing between date time editors, so it would be nice to double check that the basic functionality of all 4 new date time editors still works as expected.

[Copilot]

Pull Request Overview

This PR updates the DateTimeWithTimeZone property editor to store dates as UTC when configured in Local mode and to avoid invalid time zone validation in that mode.

• Track the configured time zone mode and skip invalid time zone validation when in Local mode
• Normalize saved value to UTC when in Local mode and adjust serialization logic
• Rename and refactor date formatting helper to accept a DateTime to format

[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

[Copilot]

Pull Request Overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[Copilot]

Pull Request Overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

[Copilot]

Pull Request Overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

[AndyButland]

This seems good to me @lauraneto - I've verified the specific issue that triggered these changes and have done a few tests with different configuration, and all seems to work as expected. I'll leave you to merge or reach out for a review first from a front-ender if you feel that is going to be useful.