Bug when updating Date objects in non-UTC timezones

[lschoeb]

Describe the bug
When editing a Date object value, the pre-filled values are not the current value.
The fields are prefilled using the displayed timezone, but the semantics of the fields are in UTC (which becomes obvious when saving).
Instead, either the Timezone should be modifiable and also pre-filled correctly OR the pre-filled values should be converted to UTC first.

Screenshots
Before:

Note: this 14:27+01 = 13:27Z

After double clicking:

Note: this is 14:27Z != 13:27Z

After saving supposedly without changes:

Note: this is not the same as in the first screenshot

Desktop (please complete the following information):

• Mingo version: 2026.2.0
• OS: macOS 15.1 (24B2082)