If you're changing your sprinkler configuration, you're doing it wrong.

Or your lawn is dying because there hasn't been enough rain. Or your lawn is dying because there's been too much rain. Or you're resodding a part of your lawn. Or you're removing part of your lawn to put in a garden. Or you've started using rainbarrels to naturally irrigate your backyard. Or your city has changed which days you can water your lawn on.

you can be pretty sure that the reason the internal clock is wrong is because the author tried to tweak things.

It could also be because the power went out or because of Daylight Saving Time.