Originally Posted by JSensei

The timer is not super accurate. I was hanging out around the 300 rank mark along with a few other active people at the end. I wanted to go to bed, but there were enough people making last ditch efforts to move into the next reward tier that I stayed up to defend my position. The timer showed about 24 minutes left when the site went into maintenance at 4 a.m.

Honestly, it worked in my favor. It allowed me to go to bed safely at 297 without letting someone get two more attacks in to push me back to 300+

It seemed pretty accurate to me considering I logged on 5 min before the event ended and the timer showed the same. Maybe you had the game open for too long :3