When releasing a version from the Project Overview > Releases, you have the option to set the Release Date. When your language is set to French, the date picker for the Release Date is corrupted, as per this screenshot:

As per above, all the values are undefined.

This problem does not happen if you are releasing the version when your language is set to English (US or UK).

This is the only date picker that is affected, the fields in other screens work fine in all languages (e.g. editing issue date fields isn't affected)