How to show current time in mac terminal prompt?
Simple answer: \T is the code for 12hr time in HHH:MM:SS. So, you'll get:

$ export PS1+="\T"
08:56:25 $
08:56:26 $
08:56:28 $
08:56:30 $


In the case you have the PS1+ is appending onto an earlier configured PS1 variable - you'll need to modify to your needs.

This is a live variable in my version of bash on High Sierra. I copied and pasted above hitting enter to show the seconds incrementing.