On T372677, we have a process that queries the revision table of all currently open and public wikis.
Out of that current set of 867 wikis, there are 10 wikis that, for some reason, have some rows in which the rev_timestamp column is full of spaces rather than having a MW timestamp as per https://www.mediawiki.org/wiki/Manual:Revision_table#rev_timestamp.
On P70617, @Krinkle did an analysis of the content of these rows for the chrwiktionary wiki , of which I copy part here:
wikiadmin2023@10.64.48.160(chrwiktionary)> SELECT rev_id, rev_page, IFNULL(rev_timestamp,"NULL") FROM revision WHERE rev_id IN (1601,1602,1604); +--------+----------+------------------------------+ | rev_id | rev_page | IFNULL(rev_timestamp,"NULL") | +--------+----------+------------------------------+ | 1601 | 1 | | | 1602 | 2 | | | 1604 | 4 | | +--------+----------+------------------------------+ 3 rows in set (0.004 sec) wikiadmin2023@10.64.48.160(chrwiktionary)> SELECT rev_id, rev_page, LENGTH(rev_timestamp) FROM revision WHERE rev_id IN (1601,1602,1604); +--------+----------+-----------------------+ | rev_id | rev_page | LENGTH(rev_timestamp) | +--------+----------+-----------------------+ | 1601 | 1 | 14 | | 1602 | 2 | 14 | | 1604 | 4 | 14 | +--------+----------+-----------------------+ 3 rows in set (0.001 sec)
There is also evidence of this issue being around at least since Jan 2015 as per T86478: Revision 1 on a wiki always shows the current time as its timestamp when rev_timestamp is blank.
The list of affected wikis is:
chrwiktionary csbwiki foundationwiki iowiki roa_rupwiki roa_rupwiktionary scwiki simplewiki tpiwiki zh_min_nanwiki
Note again our process only hits currently open and public wikis. There may be more hits on closed and/or private wikis.