You can change pm and am in your taskbar by following this steps;-

Steps:-

1:- Go to Control panel (start/control panel )
2:-switch to classic view,if it isn’t switched
3:- go to Regional and Language option
4:- click on Customize (beside English US)
5:- Go to TIME tab
6:- Change AM symbol to your name or some thing that will appear instead of AM
7:- Change Pm Symbol to your name or some thing that will appear instead of PM
8:-click on Apply and then Ok ...