Your opponent is using their vacation time.
Due to certain factors (their turn, less than 90 minutes remaining, premium member), their auto-vacation has turned on to keep them from timing out. If they don't return from vacation in ~18 days, then you'll get the win on time.
If they come back within 24 hours, then some time will be added back to their clock (this is to compensate for having a full day of vacation time removed from their bank when auto-vac kicked in).
Hi guys, I'm playing a game which should of ran out of time by now but my opponents clock has paused right on the last hour, Not sure how they did this or what's going on?