Is my clock's battery backup working?

Bought a Westclox model 70018 alarm clock from Walmart. I have to get up at three in the morning and specifically wanted one with battery backup in case of power outages. Yesterday the power did go out and the battery backup did not work. Is there a switch to set or what?

The most common concern with the battery backup is that time is not shown on the display while the power is out (running on backup battery). The clock appears to be OFF but in fact it is working to keep the alarm. The alarm will go off at the correct time, but to preserve battery power the time is not shown.

We recommend the backup battery be changed once a year, or after a power outage (whichever comes first).