PROBLEM SOLVED ? MAYBE

After trying everything in the book, I decided to set the starting time to 11:59:50.

When the time clicked over to 12:00:00, the bit changed ! !

It consistently changes on the transition from 11:59:59 to 12

That does not seem normal - but at least it works -
Did I miss something thinking that Am (or PM) changed from 11 to 12 vs 12 to 1 ?
Probably just my ignorance of the universal timekeeping protocol

Has anyone else tested this?

Ken