I'd really like an option to show all dates as yyyy-mm-dd HH:mm. The existing multitude of various things based on the age is much less workable.
Probably, at least the 3 common formats for date are needed with a check box for 2/4 digit year and a character for the separator, including no character at all:
yy-mm-dd dd-mm-yy mm-dd-yy
along with the time formats:
HH:mm HH:mm:ss HH:mm xM HH:mm:ss xM
(where the x is either A or P).