On Tuesday, one minute of the day will be 61 seconds long

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last updated 29 June 2015

If on Tuesday, June 30, the moment before the clocks strike 8 p.m. feels just a bit longer than usual, it won't be all in your head. For just one second, time will be standing still and the minute before 8 p.m. ET will not be the usual 60 seconds long — it will be 61 seconds. While the difference of one second isn't that big of a deal for most, market traders around the world are bracing themselves for the worst.

That's because there is one big difference between Tuesday's leap second and those that came before: This will be the first time that a leap second has occurred during trading hours since the markets first went electronic, Bloomberg Business reports. In a business where $4.6 million in stocks are traded worldwide every single second, one second is actually a pretty long time.

This extra second is humans' way of accounting for the slowing of the Earth's rotation to ensure the time is accurate on Coordinated Universal Time, which is based on an atomic clock. Tuesday's leap second will mark the 25th time this phenomenon has happened since 1972 and the last time we've seen it since 2012, when the leap second happened on a weekend.