Every physical Time Timer uses a quartz crystal to drive a motor which moves the colored disk as time elapses. The true duration of your timer can be up to 30 seconds shorter or up to 20 seconds longer from where the timer disk is originally set. This level of accuracy is actually quite impressive! Many common mechanical timers can have variance up to 3 full minutes! In addition, many other timers require the user to set a timer for a minimum of a 10 minute duration before the timer can even begin.
Another factor for timing variance can be your Time Timer's battery life. If you're experiencing slow timing or no movement of the disk at all, you should replace your timer's battery.
If you've changed the battery and your Time Timer is still off by more than 30 seconds, please contact us to request a replacement.
For the curious:
Many time-of-day clocks also use a quartz crystal for time keeping, but because these clocks consistently count forward, they remain rather accurate.