Select based on revision date
None of these work, it seems, at least in a simple way. For example
{{#dplvar:set|t90|{{#timel:Ymd|now - 90 days}}}}
{{#dpl:category=New works
|lastrevisionbefore={{#dplvar:t90}}
|mode=userformat
|resultsheader=%TOTALPAGES%
}}
gives a number (probably PAGES * 2) of paired Notices, referring to two deprecated fields "rev_user_text" and "rev_comment", before the display (which is correct). These fields are (were) in the Revision table (https://www.mediawiki.org/wiki/Manual:Revision_table). Similar results for other parameters like firstrevisionsince and allrevisionsbefore. MW 1.33.2 with php 7.2.32 and dpl 3.3.3. (Same result in MW 1.34.0)
Edited by Barry Johnston