Explained: The Gregorian calendar and New Year’s Day in other systems

The Gregorian calendar

This calendar was brought into use by Pope Gregory XIII, the leader of the Roman Catholic Church, in 1582, and is named after him. It is a solar dating system that reformed the Julian calendar, which had been established by the Roman emperor Julius Caesar in 45 BC.

Both the Gregorian and Julian calendars consider a solar year to comprise 365 and a quarter days. Both ‘intercalate’ or add one day every four years so that the calendars correspond to the seasons.

However, as the solar year more correctly comprises 365 days, 5 hours, 48 minutes, 45.25 seconds, the dates of seasons in the Julian calendar regressed by almost one day per century.

The Gregorian system improves the Julian system by only considering those century years as leap years which are exactly divisible by 400 (eg. 1600, 2000).

When the Julian calendar was in force, much of Europe in medieval times regarded March 25 (Feast of the Annunciation), the day nine months before Christmas, as the beginning of the new year.

The establishment of the Gregorian calendar established January 1 as New Year’s Day. England and its colonies adopted the new system in 1752.

New Year’s in other calendars

Vaisakhi, the first day in the Vikram Samvat calendar, is revered in Hinduism and Sikhism and falls on April 13 or 14.

Sikhs commemorate the formation of the Khalsa in 1699 on this day. The festival goes by different names in the parts of India where it is celebrated, such as Poila Boishakh in West Bengal and Tripura, Bohag Bihu in Assam, Vishu in Kerala, and Puthandu in Tamil Nadu.

The Islamic Hijri calendar, which follows a lunar system, consists of 354 or 355 days and begins the new year with the month of Muharram.

The Jewish calendar year begins on Rosh Hashannah, the first of the Tishri month, and falls between September 6 and October 5.