Calendars of the world

Gregory XIII

He announced the reform in the bull “Inter gravissimas”; it had been worked out by Aloysius Lilius and Christopher Clavius.

💡 Did you know? Britain and its colonies only switched in 1752.

10

Thursday 4 October was followed directly by Friday 15 October.

💡 Did you know? Today the gap between the Julian and the Gregorian calendar is 13 days.

Julius Caesar

He was advised by the astronomer Sosigenes; to bring the calendar back in line with the Sun, the year 46 BC lasted 445 days.

💡 Did you know? The month of July still bears his name.

400

That is why 2000 was a leap year but 1900 was not; this way the calendar year drifts by only a day in about 3,000 years.

💡 Did you know? The year 2100 will not be a leap year either.

622

It begins with the Hijra, Muhammad’s emigration from Mecca to Medina.

💡 Did you know? This way of counting was introduced only about 17 years later, under Caliph Umar.

354

It consists of twelve lunar months of 29 or 30 days, which is why Ramadan moves about eleven days earlier each year.

💡 Did you know? In leap years it has 355 days.

Rosh Hashanah

The name means “head of the year”; in the synagogue the ram’s horn, the shofar, is blown.

💡 Did you know? People eat pieces of apple dipped in honey so that the new year will be sweet.

13

In seven years out of nineteen an extra month of Adar is inserted so that the festivals stay in their season.

💡 Did you know? Years are counted from the traditional date of the creation of the world; the year 5786 began in autumn 2025.

Rat

Legend has it that in the great race of the animals it rode on the Ox’s back and jumped off just before the finish.

💡 Did you know? Chinese New Year falls on a new moon between 21 January and 20 February.

60

Wood, fire, earth, metal and water each apply for two years in a row; 2026 is a year of the Fire Horse.

💡 Did you know? A 60th birthday is specially celebrated in China and Japan because one has then gone once round the whole circle.

2012

On 21 December 2012 the Long Count turned over to the date 13.0.0.0.0, the start of a new baktun cycle.

💡 Did you know? For the Maya it was no end: inscriptions name dates thousands of years later.

Vendémiaire

The calendar was in use from 1793 to the end of 1805 and had twelve months of 30 days and weeks of ten days.

💡 Did you know? The name comes from the grape harvest; Napoleon’s coup of 18 Brumaire bears one of these month names.

November

Russia still used the Julian calendar: 25 October was 7 November 1917 by Gregorian reckoning.

💡 Did you know? The Soviet Union therefore celebrated the anniversary on 7 November.

Nicaea

Easter falls on the first Sunday after the first full moon of spring, so it lies between 22 March and 25 April.

💡 Did you know? Because most Eastern churches still reckon by the Julian calendar, they often celebrate Easter on a different day.

Thor

The Germanic peoples took over the Roman day names and put their own gods in: the day of Jupiter became the day of the thunder god.

💡 Did you know? Saturday is the only English weekday still named after a Roman god, Saturn.

Joseph Scaliger

The count starts on 1 January 4713 BC, so events can be converted across all calendars without gaps.

💡 Did you know? Its day begins at noon, so that a night of observation is not split between two dates.