It's not happened to me lately, last time was like a year ago (and I'd only liked like 4 posts consecutively). I just usually see it happen to users who go on a like rampage. Coulda just been a hiccup with xenforo tho.
It happens if the page hasn't loaded fully (html and css has been retrieved, but not the JS), so the buttons take you to the full page for their function instead of running in the background. The same thing happens when you have JavaScript disabled.
As for dates, theyre loaded as full dates to start with, and later populated to the short version through a script.
Note that the page not loading fully can be caused from a variety reasons, like your internet being slow, gbatemp servers being slow or just a freak error that prevented the scripts from being downloaded for some random reason.