The year 1972 was the longest in modern history. It was a painful 31,622,402 seconds

To measure time, the world uses highly accurate atomic clocks, which would only drift by about a second every million years. But from time to time, we need to add a little extra second to make sure our time matches the sky. And 1972 had a jackpot…

The year 1972 was particularly long. Not exactly because it was very boring, but because it was literally bigger than usual.

1972 was a leap year, so it already had another 24 hours than ordinary years. Furthermore, additional two intercalary seconds: one on June 30th and another on December 31st — which made it 24 hours and 2 seconds longer than “normal”.

In total, 1972 had 31,622,402 secondscompared to the 31,536,000 seconds of a common 365-day year, and the 31,622,400 seconds of a conventional leap year.

Os intercalary seconds are added to keep our clocks synchronized with the slightly irregular rotation of the Earthexplains .

Currently, the world uses atomic clocks to measure Coordinated Universal Time (UTC). These high-precision instruments are based on natural vibrations of atoms, usually cesium. Each cesium atom oscillates exactly 9,192,631,770 times per second.

By counting these oscillations, atomic clocks measure time with such accuracy that would only deviate by about a second after millions of years.

However, these ultra-certified watches are not perfectly aligned with the position of the Sun in the sky, since the Earth does not rotate completely regularly from one day to the next.

Therefore, from time to time, we need to add a small extra second to ensure that our time matches the sky.

Although the millisecond variations may seem insignificantare crucial for technologies that rely on extremely precise timing, such as GPS navigation, telecommunicationsfinancial transactions and certain scientific experiments.

To bridge this potential gap, the first intercalary second it was introduced in June 1972, following an international agreement. To make up for lost timeended the year with another interim second, added in December.

Since the 1970s, they have been added to the whole less than 30 seconds interleaved to UTC to maintain balance between atomic clocks and the Earth’s rotation, with 1972 was the only year in which two distinct intercalary seconds.

Typically, an interim second is added on June 30th or December 31st. In 1972, This occurred on both dates because the Earth’s rotation had unusually sharply out of phase compared to atomic time, the result of decades of accumulated deviation and lack of correction.

The year 1972 must retain the title for some time “longest year”. The Earth’s rotation has actually accelerated in recent years, making the days .

As a consequence, it may be necessary to “negative intercalary second” to adjust UTC to astronomical time. That is, those responsible for measuring time will subtract a leap second in order to ensure that atomic clocks remain in tune with the astronomical movement of the Solar System.

But the title of “longest year in history” naturally depends on how defines what a year is. Will it be a measurement associated with a universal movement or something more human?

If we choose this perspective, then the “longest year ever” is not 1972, but the called “year of confusion”. At the time, the Roman emperor Julius Caesar, advised by his astronomers, added a few days to the calendar, to align it with the solar year — and 80 more than we are used to.

And the shortest year ever, what was it? It would have been 1582, the year in which the month of . Due to the transition from the Julian calendar to the Gregorian calendar, the tenth month jumped from the 4th to the 15th.