First leap second added to UTC - June 30, 1972

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Today June thirtieth twenty twenty. The Day was June thirtieth nineteen seventy-two. At eleven fifty nine PM. In sixty seconds, a leap second was added to coordinate universal time to synchronize clocks with earth decelerating rotation. The second has been defied many different ways over the years at one point, it was defined as one eighty, six, thousand, four, hundred of the mean, solar day, but more precise measurement was needed because the length of day varies depending on many factors like seasonal daily weather variations as well as. In atmosphere tides. By nineteen, sixty seven, the second was defined as and I quote the duration of nine, billion, one, hundred, ninety, two, million, six, hundred, thirty, one, thousand, seven, hundred and seventy periods of the radiation, corresponding to the transition between the two hyper fine levels of the ground state of the Caesium went thirty three atom. This was the measurement that the international system of units or as I used since thin. The wording of the official definition has been updated slightly. Atomic clocks keep time with. Precision on atomic clocks, a day is exactly eighty six thousand four hundred PSI seconds. International Atomic time is a timescale that is computed by taking the weighted average of more than four hundred atomic clocks around the world. It's not connected to any astronomical observations. Universal time on the other hand is a time standard that is based on earth, rotation and astronomical observations coordinated universal time or ut is under the umbrella of universal time, which also includes ut zero ut, wine, ut, when our and ut to unlike other versions of Universal Time Utd is determined by International Atomic time. Though the practice of ut was already being coordinated internationally. The International Astronomical Union didn't adopt the name coordinated universal time until nineteen sixty seven. Coordinated. Universal time is the primary standard by which the world regulates time. But Earth's rotation as measured by UT, one is gradually slowing so that the length of a rotational day is about two milliseconds longer than the eighty six thousand four hundred seconds. It was two centuries ago. That means that there's a discrepancy between ut. See in ut wine. Scientists determined that Ut. To count for the difference between the definition of the second Earth's rotation, this keeps ut in line with the apparent position of the Sun and Stars in other words, a second would need to be added to or removed from clocks to realign them with patient occasionally. Scientists specified that you TC shows deviate more than nine tenths of a second from ut one so on June thirtieth nineteen, seventy, two. The I league second was added to ut. The international earth rotation in reference. System Service decides went at a leap. Second one is typically added either on June, thirtieth or December thirty first. From nine hundred seventy to one thousand, nine hundred nine leap seconds per at it at a rate of about one per year after that they've been added less frequently, there have been twenty-seven leap seconds since nineteen seventy two, the most recent leaf second was added on December Thirty First Twenty sixteen. Many people have called for the elimination of leaks, seconds, and the replacement of ut see with a new system leap seconds have caused problems for some computer systems since they're not that predictable can't be anticipated far in advance. And they'll need to be added more frequently as Earth's rotation continues to slow down. Some people who support abolishing leap seconds argue that it doesn't matter whether our perception of time changes along with the rotation of earth since that would happen over a long time anyway.

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