It does use a couple of timers but most of them are relatively long lived:
1. Day change timer: Fires once a day at midnight to update labels
2. Reload event timer (if the calendar doesn't change this timer fires after the maximum look-ahead time and +- 12 hours)
3. Expiry timer (fires every time soon as the first event expires)
4. Calendar close timer (to prevent constant reloading of the calendar backend in case a lot of items are being edited - it is only activated if the calendar was previously changed)

Timer 1 & 2 should be negligible for power consumption. 3 & 4 could be more problematic but should not have a noticable impact on battery life. The issue with global timers is the interval in which they should be run and whether the daemon will not end up being the only process waking up the system in that case. I will look into adding that functionality in the next version. Thanks for letting me know.