Why do pro umps carry stopwatches?

[jbucks]

Why is that every so often, after an inning ends, you'll see a base umpire pull out a stopwatch from his pocket? This makes zero sense to me.

[guyinaredhat]

Durring a televised game they use the stop watch to make sure the innings get started not too early and not too late.  College umpires use a stop watch cause there's a time limit between innings.