Waking before sunrise March 12? Daylight saving time could affect your scheduled alarm

For runners, there’s a lot to do the night before a big race: selecting an outfit, curating a playlist, getting a good night’s sleep. And, particularly if the race coincides with daylight saving time: setting the alarm accordingly. 

"It is DAYLIGHT SAVING TIME on Race Day!" read an email sent to a PolitiFact staff member. 

"Your clocks will spring forward from 1:59 a.m. to 3:00 a.m.," read the email. "Remember that NO alarm set for the 2:00 a.m. hour will go off! If your plan requires you to wake up any time from 2:00 a.m. to 2:59 a.m., you MUST set your alarm for the 1:00 a.m. hour."

Runners who don’t adjust their alarms might risk missing their start times. But whether "no alarm set" within the 2 a.m. hour will work as planned depends on the type of alarm.

Daylight saving time refers to the practice of setting clocks forward an hour in the spring, to create more sunlight hours in the evening at the time of year when the weather is warmest. It was introduced during World War I as a way to conserve electricity. 

There have been attempts to stop the practice, but aside from Hawaii and the majority of Arizona, the only two states that do not observe daylight saving time, none have stuck. 

This year, daylight saving time begins at 2 a.m. local time March 12. 

That means at 2 a.m. "the local time skips ahead to 3 a.m., so there is one less hour in the day," according to the National Institute of Standards and Technology. 

Generally, clocks in Android phones and iPhones will automatically change to daylight saving time. 

The website Android Help said that choosing the "set time zone automatically" feature in settings will signal to Android phone clocks to adjust times automatically.

"Unless you have a really old Android phone or if you have previously meddled with the time and date settings, you shouldn’t have to do anything," wrote Android Central, a site dedicated to news and reviews of Android devices.

Apple’s support website said iPhones often automatically adjust for time zone changes and daylight saving time. The site said iPhones or iPads must have fully updated software and "set automatically" must be switched on in the "Date & Time" settings. 

In some cases, however, Apple said people with certain phone carriers or who live in certain regions cannot turn the "set automatically" option on or off. And of course, technology glitches are always possible. 

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The chain email appears to be partially correct in its warning: If commitments require waking up between 2 a.m. and 2:59 a.m., not every device will respond the same way.

When the clock strikes 2 a.m., on devices that adjust automatically, the time will spring forward to 3 a.m. 

"Two a.m. continues to exist, but in an abstract sense," said Jeff Sherman, a researcher in the National Institute of Standards and Technology’s Time and Frequency Division. 

That means it’s possible alarms set for 2 a.m., or any time within the hour, won’t sound. 

Some devices prevent you from setting such alarms. A PolitiFact reporter asked "Alexa," the voice of the Amazon Echo smart speaker, to set an alarm for 2:30 a.m. on Sunday, March 12. Alexa responded: "I couldn’t set your alarm because of the daylight saving time change." 

Other reporters asked Apple and Android phones to set reminders, because you can’t set alarms more than a day early. Siri set an iPhone reminder for 3 a.m. after being asked to set one at 2:30 a.m. March 12. The Android phone set a reminder for 3 a.m. instead of 2 a.m. 

In other cases, devices might automatically adjust the alarms in tandem with the clock.

"While the behavior will depend on which Android app you are using to set the alarm, Google's official Clock app, which is preloaded on Pixel and other Android devices, will automatically move the alarm to a new time," said Google spokesperson Kaori Miyake. A 2:01 a.m. alarm would go off at 3:01 a.m., for example. 

Apple did not respond to a request for comment.

Sherman suggested early risers could also set a "countdown timer" that will ring at the appropriate time regardless of the daylight saving transition.

An email claimed that on March 12 when daylight saving time begins, "NO alarm set for the 2:00 a.m. hour will go off!"

Cellphone clocks typically adjust automatically. Some Android devices will automatically adjust alarms set on certain apps within the 2 a.m. hour to instead go off in the 3 a.m. hour. 

And some clocks — including some alarm clocks — need to be manually reset.

The statement is partially accurate but leaves out important details. We rate it Half True.  

PolitiFact Staff Writers Grace Abels and Gabrielle Settles contributed to this report.