NOEL KING, HOST:
All right. You know how we set our clocks ahead in March, springing forward, as they say? But does that mean we started or ended daylight saving time? Let's ask an expert.
(SOUNDBITE OF FILM, "BACK TO THE FUTURE, PART II")
CHRISTOPHER LLOYD: (As Doc Brown) The time continuum has been disrupted, resulting in this alternate reality.
STEVE INSKEEP, HOST:
Wait. Wait. Wait - not that expert, not Doc Brown from "Back To The Future." Let's go to a real-life time machine keeper.
DEMETRIOS MATSAKIS: My name is Dr. Demetrios Matsakis. I worked for 40 years at the U.S. Naval Observatory, most of that in timekeeping.
INSKEEP: Matsakis was one of the scientists in charge of the U.S. Naval Observatory Master Clock.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED PERSON: U.S. Naval Observatory Master Clock - at the tone, Eastern Daylight Time, seven hours, 55 minutes, 15 seconds.
(SOUNDITE OF BEEP)
KING: That master clock keeps the internet, cellphones, GPS devices and other gizmos in sync right down to the nanosecond.
MATSAKIS: A nanosecond is a billionth of a second. Time is the most accurately measured quantity that humans have come up with.
(SOUNDBITE OF LEROY ANDERSON SONG, "THE SYNCOPATED CLOCK")
KING: But it's still really confusing, keeping standard and daylight time straight. Matsakis says you can see the problem this time of year when people try to schedule meetings across time zones.
MATSAKIS: The meeting was being scheduled in Europe. And I wasn't sure the Europeans were aware the Americans switched to daylight time different days of the year than the Europeans do.
INSKEEP: Meeting times are often typed as EST, Eastern Standard Time, when they actually mean EDT, Eastern Daylight Time.
(SOUNDBITE OF SONG, "DOES ANYBODY REALLY KNOW WHAT TIME IT IS")
CHICAGO: (Singing) Does anybody really know what time it is? Care - does anybody really care about time?
INSKEEP: Here's a trick to help you remember. There's more daylight during the summer, so if you set the clocks ahead, you're on daylight saving time. When you fall back, you're on standard time.
KING: And yet, inevitably, Matsakis says it's about to get a lot more confusing.
MATSAKIS: Europeans - the EU took a vote, and it was pretty overwhelmingly in favor of no more switching back and forth. They haven't implemented yet, but some countries are going to go on permanent daylight time, and other countries are going to stay on standard time. Could be very confusing to keep track of which ones are doing which.
(SOUNDBITE OF SONG, "CHANGES")
BUTTERFLY BOUCHER: (Singing) Time may change me, but I can't trace time.
KING: Matsakis says you shouldn't get stressed over time. In fact, he doesn't even wear a watch.
(SOUNDBITE OF SONG, "IF I COULD TURN BACK TIME")
CHER: (Singing) If I could turn back time, if I could find a way... Transcript provided by NPR, Copyright NPR.