Today is February 29, 2016. Watch geeks worldwide are excited to see their perpetual calendar timepieces account for the extra day. But what they might not know is that most of their watches have already been a second off since June 30, 2015.

That’s because of something called a leap second. Irregularities in Earth’s rotation cause time as we know it to get off track. Since 1972, we’ve been accounting for this lapse in time by inserting an extra second into the system. There have been 26 of these leaps. Scientists might be able to explain it better:

The reason we have to add a second every now and then, is that Earth’s rotation around its own axis, is gradually slowing down, although very slowly.  Atomic clocks, however, tick away at pretty much the same speed over millions of years. Compared to the Earth’s rotation, atomic clocks are simply too consistent. –timeanddate.com

For time-OCD collectors, the Seiko Astron (and this) is smart enough to keep track of leap seconds on its own. See for yourself:

A video posted by KeepTheTime (@keepthetime) on


The Astron gets the time right no matter where you are in the world – and no matter what “leap” it is. This is all thanks to an exclusive Seiko ring antenna located directly under the dial. With the ring, your watch connects to four or more satellites and updates the time on your behalf. It even automatically adjusts the time as you fly over different time zones.

The GPS module in the Astron operates via solar power, no batteries needed. If James Bond were to go back to using a Seiko, this is the watch he’d be wearing.

Recommended reading: What to know about a Perpetual Calendar watch?

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