Reduce countdown timer resolution to minutes

Updating the countdown timer once-per-second is inefficient. The actual marathon start will probably not be accurate to the minute, let alone to the second. Consuming 60 times the CPU for per-second updates isn't worthwhile.

I added code to schedule the countdown timer for per-minute updates, rather than per-second. Note that this only changes the timer, not the display, which still includes seconds. I was also coding without a Java compiler, so I don't even know if this works. If it does, however, you can remove the seconds from the countdown display.