Dates have to be formatted year, month, date; zero-padded, no punctuation. If you did it right, you should have a total of eight digits. The New Year's Day 2007 (Gregorian Calendar) would be formatted as 20070101, for example.
Comparison and understanding
Today is Thursday, February 25, 2021.
In digits, this would either be 02/25/2021 (USA) or 25/02/2021 (majority of the world).
Formatted correctly for the template, it would be 20210225.
Date format = YYYY (4 digit Year) MM (2 digit Month) DD (2 digit Day)