Forked from T57755 . On Commons the maximum precision allowed to enter is currently 11 (day). Please increase this to 14 (second). The imageinfo extension should probably override the time data type to always set the timezone to null instead of 0 to make it clear that not all times are UTC.
This mirrors the current practice on Commons, see for example https://commons.wikimedia.org/wiki/File:Northstar_California_Prosser_2.jpg where the date field contains "2017-07-03 13:28:12".