I've seen this happen a couple of times, didn't think any of it but now I'm starting to wonder if it's an actual issue.
Sometimes when I check my subscribed threads it'll say a new post has been added, even though it was post that is anywhere between 5-10 hours old. That wouldn't really bug me but the time stamp on the post is off by that 5-10 hour difference.
Here's a screenshot of what I mean. The time stamps are circled in red.