There seems to be a discrepancy between the times on the main Wanted-Players forum page and the posts within the threads.

I posted a reply to an ad in the Wanted-Players forum.  The post itself says it was posted Sat 19 Apr 2014 at 14:56.  This is correct as far as time and date go for my timezone.  But on the main page of the forum, it says the last post was "08:54, Yesterday by Evil Empryss".  Today is still the 19th, for about four more hours in the time zone I'm in, and the time stamp is way off.

Sounds like bump calming in effect.

I'm not sure what that means, but it sounds like you're saying it's supposed to do that.  Okay.

I was concerned that it would throw off the timing for the whole "one bump per week" thing if it wasn't tagging the last post correctly.

Yes, it's supposed to be like that.  :)  In the information box at the top of the ad, it says

The last comment date/time on the forum menu refers to the last valid bump (in this case the original post in the thread).  It won't affect the date for bumping, as the thread will not be available for a bump until at least seven days after that last "bump".