time zone not displaying properly

[ reminder: don't post multiple *same topics ]

i initially posted this 3 days ago in the "script/code" problem forum. not sure if i goofed and submitted post in wrong place and apologies if i had.. some sort of reply ,even if it was to say i posted my inquiry in the wrong place, would have been considerate..
problem:although i set my time zone via the admin panel to reflect the zone in which i reside, it will not display the proper time in the forum or its post. I am aware of how and am 99.9 % sure i had done so correctly. of my three sites, this is happening to 2 of them..Although i find it on the bottom of the list of things that can go wrong, It's has become a guessing game when a post was written. Any idea whats happening or what i can do to sort said problem ? if i set to display "am", it shows "pm" in site and in the messages..
while i'm on here; how in Gods green earth do i erase the posts in the chat box? sometimes it's the easiest of things can be the most difficult. why is that.