It's important to pay attention to daylight savings time.
Daylight savings time starts tomorrow and Dan needs to work in the morning.
Dan wants to go to work.
Dan changes his clock and wakes up an hour early to get ready for work.
Dan doesn't change his clock and wakes up at the usual time to get ready for work.
Dan arrives on time, making his boss happy.
Dan arrives an hour late, exasperating his boss.