The days that vanished and the switch to the Gregorian Calendar

As all we known, Julius Caesar was a brilliant Roman general. Born of a patrician family, he rose through the political and military ranks of Republican Rome to become Consul in 59BC, establishing control of Rome by forming the so-called First Triumvirate with Pompey and Crassus. Appointed Governor of 4 legions he conquered Gaul greatly extending Rome’s empire. In 49BC Caesar, refusing to give up his command he crossed the Rubicon and ignited civil war. Appointed Dictator of Rome in 48BC he defeated his opponents before instigating a series of reforms. Eventually, he was assassinated in Rome on the Ides of March by a group of conspirators and his death led directly to the end of the Roman Republic and the establishment of the Roman Empire under Caesar’s heir Augustus.

However…. Julius Caesar he wasn’t very good at sums. And the calendar that he devised in 46 BC, named the Julian calendar in his honour, was flawed, even though it was to last for 1,600 years.
The problem?
Caesar had calculated that a year lasted for 365 days and six hours, but this did not properly reflect the actual time it takes the Earth to circle once around the Sun, known as a tropical year.
In fact it is only 365 days, five hours, 48 minutes and 45 seconds. Not much difference, apparently, but enough, “just” 1,600 years later, to have put the world astray by a whole week….
So it was on this day, October 4, 1582, such as Ugo Buoncompagni, an Italian better known as Pope Gregory XIII, introduced a new calendar, the Gregorian calendar, which would iron out the Julian discrepancies. Eventually it become widely accepted and is the calendar in use today across much of the world.

Gregory needed to lose a few days so under his new system October 4, 1582 was followed the next day by 15 October, and he decreed that New Year’s Day should be moved from 1 April to 1 January.
Then there was the question of leap years – those containing 366 days and necessary to keep the calendar in alignment with the Earth’s revolutions around the Sun. Thus, Gregory calculated that if we didn’t add a leap day on February 29 nearly every four years, we would lose almost six hours off the calendar every year. As a result, after only 100 years it would be astray by 24 days!
In addition, he also modified Caesar’s concept of a leap year precisely every four years, which is too many: the Gregorian calendar uses in fact a much more accurate method for calculating leap years and stipulates that century years, even though divisible by four, are not leap years. The exceptions are those that can be divided by 400. Thus, 2000 was a leap year, but 1900 not.
The Gregorian calendar was to become accepted worldwide, even though some countries stuck out for Julian. The UK did not accept Gregory until 1752, whereas Greece held out until 1923. The last convert was Turkey, which accepted the Gregorian calendar in 1927.

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