HISTTIMEFORMAT

3.4.2. Build-in Variables
3.4.2.1. Editing mode variables

HISTTIMEFORMAT="%y/%m/%d %T "

...
78 04/11/26 17:14:05 HISTTIMEFORMAT="%y/%m/%d %T "
79 04/11/26 17:14:08 ls -l
80 04/11/26 17:14:09 history

echo "$HISTTIMEFORMAT"
%y/%m/%d %T