History & Origin

The Gregorian calendar was introduced by Pope Gregory XIII on 15 October 1582 as a reform of the older Julian calendar. The Julian calendar had a small error — it added a leap day every 4 years without exception, causing a drift of about 10 days over the centuries. By the 16th century, the spring equinox was falling on 11 March instead of 21 March, disrupting the calculation of Easter.

Pope Gregory XIII, working with mathematician Christopher Clavius and astronomer Luigi Lilio, corrected this by skipping 10 days in October 1582 (the day after Thursday 4 October became Friday 15 October) and refining the leap year rule. Catholic countries like Spain, Portugal, Poland and Italy adopted it immediately. Protestant and Orthodox countries followed much later — Britain and its colonies (including America) adopted it in 1752, and it was not universally adopted worldwide until the 20th century.

Pakistan, as a successor state of British India, uses the Gregorian calendar for all official, legal, business and educational purposes. The Islamic Hijri calendar is used for religious dates.

Structure of the Gregorian Year

The Gregorian calendar has 12 months, divided into four quarters. The year has either 365 days (common year) or 366 days (leap year). A year is a leap year if it is divisible by 4, except for century years which must be divisible by 400. So 2000 was a leap year, but 1900 was not. The next leap year after 2024 is 2028.

Seasons in 2026

The four seasons are determined by the Earth’s position relative to the Sun. The equinoxes and solstices mark the official beginning of each season in the Northern Hemisphere. Note that seasons are reversed in the Southern Hemisphere (e.g. December is summer in Australia).

Month Name Origins

January — Named after Janus, the Roman god of beginnings, doorways and transitions, who is depicted with two faces looking to the past and future.

February — From the Latin februum, a Roman purification festival held on 15 February. It is the shortest month, a remnant of when the Roman calendar had only 10 months and winter was uncounted.

March — Named after Mars, the Roman god of war. This was originally the first month of the Roman calendar, which began in spring.

April — Possibly from the Latin aperire meaning “to open”, referring to the opening of flowers in spring. Others suggest it derives from Aphrodite, the Greek goddess of love.

May — Named after Maia, the Roman goddess of spring and growth, daughter of Atlas.

June — Named after Juno, the queen of the Roman gods and goddess of marriage, making it considered an auspicious month for weddings.

July — Named in honour of Julius Caesar, who reformed the Roman calendar. He was born in this month (then called Quintilis, meaning “fifth”).

August — Named after Emperor Augustus Caesar, the first Roman emperor. Originally called Sextilis (sixth month).

September, October, November, December — Named after the Latin numbers 7 (septem), 8 (octo), 9 (novem) and 10 (decem). They retain their number names from the old 10-month Roman calendar that began in March, even though they now fall in positions 9 through 12.

Gregorian vs Other Calendars Used in Pakistan