The following table outlines the format specifiers that can be used with the $dateToString aggregation pipeline operator in MongoDB.

Specifier	Description	Possible Values
%d	Day of Month (2 digits, zero padded)	01–31
%G	Year in ISO 8601 format	0000–9999
%H	Hour (2 digits, zero padded, 24-hour clock)	00–23
%j	Day of year (3 digits, zero padded)	001–366
%L	Millisecond (3 digits, zero padded)	000–999
%m	Month (2 digits, zero padded)	01–12
%M	Minute (2 digits, zero padded)	00–59
%S	Second (2 digits, zero padded)	00–60
%w	Day of week (1-Sunday, 7-Saturday)	1–7
%u	Day of week number in ISO 8601 format (1-Monday, 7-Sunday)	1–7
%U	Week of year (2 digits, zero padded)	00–53
%V	Week of Year in ISO 8601 format	01–53
%Y	Year (4 digits, zero padded)	0000–9999
%z	The timezone offset from UTC.	+/-[hh][mm]
%Z	The minutes offset from UTC as a number. For example, if the timezone offset (+/-[hhmm]) was +0445, the minutes offset is +285.	+/-mmm
%%	Percent Character as a Literal	%

The above table is based on the table from the MongoDB documentation for the $dateToString operator.