The creation date specified during the upload of a file is not linked to any specific time zone. However, UploadWizard ignores the existence of time zones with positive UTC offsets.
Problem: If I am in UTC+02 and it is less than 2 hours after midnight, the calendar widget correctly suggests "today" by framing the day in the month calendar and I can choose that date. However, when I submit the form, I get a warning saying "The date that you selected is in the future." The probable cause is that this date has not yet come in the UTC time zone. The date may, however, be valid in some or all of the time zones that are ahead of UTC.
Suggested solution: Do not issue a warning if specified date is a current or past date in any place of the world – simplified, it currently means use UTC+14:00 for checking.
Observation: Properly defining my time zone in Preferences - Appearance does not make any difference.