'Last Post' time info inconsistancy

Just noticed inconsistancies in the display of the time that a post was submitted.
I have the last posted items saying it is xPM Today, when it is still only AM. I checked my Board settings and local time is correct...AM. On the main forum index the last post time seems to be correct, but when I click that thread, there may be perhaps a few threads on top of the list, indicating PM which are later postings, and the time on the post that I clicked is now different. Hard to explain because nothing seems to match up. Very strange.
Julie