Remember the phrase "spring forward, fall back." In the spring, you adjust your clocks one hour forward, and in the fall you adjust them one hour backwards. This always happens at 2 am on a Sunday, so tomorrow morning at 2 am you turn the clock back to 1 am.

Of course if you're not going to be up that late you can just do it when you go to bed tonight, and most phones, cable boxes and computers do it automatically (if they're set to the right time zone.)

The actual date this happens on can change, so you have to find out about it from a news site or the tv news. So lots of people forget and do it the next day when they notice their clocks are wrong.