Tonight's the night!! When you change your clock don't forget to change your batteries in your smoke alarms and carbon monoxide (CO) alarms. While you're at it, check the age of your alarms. On the back of the smoke or CO alarm, you should see a manufacture date. If the smoke alarm is 10 years old or older, it needs to be replaced. If the CO alarm is 5 years old or older, it needs to be replaced. If there is no date, your alarm is old and needs to be replaced. Fresh alarms, and fresh batteries - don't go to bed without them!