Regretfully, timers are not 100% accurate.
regular timers, which are set to the second can (and do) actually trigger with up to a 1 second variance.
This can be reduced by using a millisecond timer.
I seem to recall this situation being reported earlier, but I don't recall when... Sorry.
Thus an intermediate solution maybe to use the -m with or without the c switch, which will keep the timer even more accurate.
