Today will be a long day. No, not because your schedule will be hectic more than ever, and not because some nugu will torture the crap out of ya, but because our time scale isn’t perfectly synchronized with the not so smooth earth’s rotation. To explain, let’s start with the leap year.
Every four years we get an extra day normally known as February the 29th. This is because the earth doesn’t actually take 365 days to journey around the sun but rather it takes roughly 365.242199 days to make one revolution. To take care of the 0.242199 days lost each year, we add one extra day every four years to the month of February on the Gregorian calendar.
It’s not just the revolution around the sun that affect time (in days lost) but earth’s rotation on its own axis also affect time in seconds lost. For example, for the past several centuries, the length of the mean solar day has been increasing by about 1.4–1.7 milliseconds per century. If nothing is done to rectify the difference between the mean solar day (time) with the atomic time that we use to reckon the time of the day, then it will happen that one day in the far future clocks will read midnight when the sun is up in the middle of the sky at exactly noon.
To avoid such a confusion, the International Earth Rotation and Reference Systems Service (IERS), since 1972, has been adding one second every once in a while to the hour just before midnight of either December 31st or June 30th. In June 30th 2012, such a second was added and three years later today, for the 26th time, IERS will be adding another second such that tonight’s 11 pm will not be 60 seconds long but will rather have 61 seconds.
No, your watch will not automatically read 11:59:60 before jumping to 00:00:00 a second later, you will have to manually reset the watch if it is the non-Internet connected type or if it is a smart watch, then it will automatically synchronize with the Internet over the coming hours. Most probably, the watch will follow Google’s route where instead of adding a second to any hour, it will be gaining milliseconds progressively until it has gained the second throughout the day.
The leap second will go unnoticed by majority of us but not for those whose trade involves precision in timing. The Verge explains that “In New York, where the leap second is scheduled to be added at around 8PM, stock markets are simply closing early to avoid headaches. Nasdaq will stop trading at 7:48PM, and shut down at 7:55PM, while both Intercontinental Exchange Inc. and CME Group are delaying data transitions during the period.” “n an environment where market values fluctuate and deals are done in tiny fractions of time, a rogue second could potentially affect millions of dollars, but for most internet users, the leap second should be added without too much of a hitch”.