Template dialog UI should respect the date locale settings

[nishantwrp]

@nishantwrp sorry to reopen an old thread but I am also encountering this on Linux.
All the documentation I found seems to indicate that the template dialog should respect the Tools > Options > Date format which I have set to YYYY-MM-DD, but it doesn't.

(Is this a UI bug?)

In the template I have:

---
start_date: date
end_date: date

I have tried to set LC_TIME and to change the date format and language of the interface but neither seem to have an effect.

I also tried to replace start_date: date with other variants, including custom_datetime but none were supported types.

Is there any other way to ensure the template shows a date format consistent with the settings?

Originally posted by @unode in #87