Currently, entering "20. century" will result in the timestamp +00000002000-01-01T00:00:00Z with the precision set to "century"[1]. However, with Ia1692d1241 applied, this will render as "19. century", since the 20. century only started with the year 2001.

So, "20. century" should result in the timestamp +00000002001-01-01T00:00:00Z, with precision "century" (and before=0 and after=1), to accurately represent the century between the start of 2001 and the end of 2100.

The same applies for millennia. Note that decades as well as anything up from precision = 10000 years is counted differently.

[1] https://www.wikidata.org/w/index.php?title=Q4115189&diff=160572560&oldid=160505889

Version: unspecified
Severity: critical