When setting a date/time format in a widget, you can use the following codes to define it :
%a: Short weekday, like 'Mon'
%A: Long weekday, like 'Monday'
%d: Two digit day of the month, 01 to 31
%e: Day of the month, 1 through 31
%w: Day of the week, 0 through 6
%W: Week of the year, starting with the first Monday as the first week, like 46 for the 46th week of the year beginning with a Monday
%V: Week number of the year (ISO-8601:1988 standards), starting with the first week of the year with at least 4 weekdays, with Monday being the start of the week, 01 to 53 (where 53 accounts for an overlapping week). Combine it with the %G year representation.
%b: Short month, like 'Jan'
%B: Long month, like 'January'
%m: Two-digit month number, 01 through 12
%y: Two-digit year, like 09 for 2009
%Y: Four-digit year, like 2009
%G: Four-digit year going by ISO-8601:1988 standards, like 2008 for the week of January 3, 2009
%H: Two-digit hours in 24h format, 00 through 23
%k: Hours in 24h format, 0 through 23
%I: Two-digit hours in 12h format, 00 through 11
%l: Hours in 12h format, 1 through 12
%M: Two-digit minutes, 00 through 59
%p: Upper-case AM or PM
%P: Lower-case AM or PM
%S: Two-digit seconds, 00 through 59
%L: Milliseconds
For example, for the 01/01/2020 date, if you define the format as ā%Y-%m-%d %H:%M:%Sā the result displayed will be : 2020-01-01 00:00:00