Updates: Status: Invalid Comment #1 on issue 284 by dorma...@rydia.net: wrong unix time http://code.google.com/p/memcached/issues/detail?id=284
Swear I commented on this before...memcached internally uses a monotonic clock, so the time changing outside of it won't change and break relative object expirations. Except if your clock is off when it starts, it'll be stuck that way.
I assume that's what's going on here, anyway.