Calendars Around the World — From Gregorian to Hijri

While the Gregorian calendar dominates international business and daily life in most countries, billions of people around the world also use other calendar systems for religious observances, cultural events, and official purposes. Here’s a tour of the world’s major calendars.

The Gregorian Calendar

Introduced by Pope Gregory XIII in 1582, the Gregorian calendar reformed the older Julian calendar by correcting its slight overestimation of the year’s length. The Gregorian year averages 365.2425 days, achieved through the familiar leap year rules: divisible by 4, except centuries unless also divisible by 400.

Today, the Gregorian calendar is the internationally accepted civil calendar. It organizes the year into 12 months of varying lengths (28-31 days) and serves as the basis for ISO 8601.

The Islamic (Hijri) Calendar

The Islamic calendar, or Hijri calendar, is a purely lunar calendar with 12 months alternating between 29 and 30 days, giving a year of approximately 354 days. Because it’s about 11 days shorter than the solar year, Islamic months gradually cycle through all seasons over a period of roughly 33 years.

The calendar begins from the Hijra — the Prophet Muhammad’s migration from Mecca to Medina in 622 CE. Important Islamic observances like Ramadan, Eid al-Fitr, and Eid al-Adha are determined by this calendar. Saudi Arabia and several other countries use it for official purposes alongside the Gregorian calendar.

The start of each month traditionally depends on the actual sighting of the crescent moon, which is why dates for events like Ramadan can vary by a day between different regions.

The Hebrew Calendar

The Hebrew calendar is a lunisolar calendar — it follows lunar months but adds an extra month (Adar II) seven times in every 19-year cycle to stay aligned with the solar year. This ensures that festivals like Passover always fall in spring.

The Hebrew year count begins from the traditional date of creation, making the current era around year 5786-5787. Israel uses the Hebrew calendar for religious observances and national holidays, while the Gregorian calendar is used for civil and business purposes.

The Chinese Calendar

The traditional Chinese calendar is also lunisolar. Months begin on the new moon, and an intercalary (leap) month is periodically added to keep it synchronized with the solar year. The Chinese New Year, the most important holiday in Chinese culture, falls on the second new moon after the winter solstice — typically between January 21 and February 20 on the Gregorian calendar.

The Chinese calendar features a 60-year cycle combining the 12 zodiac animals (Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig) with five elements (Wood, Fire, Earth, Metal, Water). While China officially uses the Gregorian calendar, the traditional calendar remains essential for festivals, astrology, and cultural observances throughout East Asia.

The Hindu Calendar

There is no single Hindu calendar — India has numerous regional variants. The two major types are the solar calendars (used mainly in Tamil Nadu, Kerala, and Bengal) and the lunisolar calendars (used in most of North India).

The Indian national civil calendar, the Saka calendar, was officially adopted in 1957 to unify India’s diverse calendar traditions. It follows a solar year beginning on March 22 (March 21 in leap years), with months of fixed lengths. However, most Hindus continue to use their regional calendars for festivals and religious observances. Diwali, Holi, Navaratri, and other major festivals are dated according to these traditional calendars.

The Ethiopian Calendar

Ethiopia uses its own unique calendar, which is approximately seven to eight years behind the Gregorian calendar. The Ethiopian calendar has 12 months of 30 days each, plus a 13th month (Pagume) of 5 or 6 days. The year begins on September 11 (or September 12 in Gregorian leap years).

This calendar is based on the Coptic calendar and ultimately derives from the ancient Egyptian calendar. Ethiopia is one of the few countries where a non-Gregorian calendar remains the primary civil calendar.

The Persian (Solar Hijri) Calendar

Iran and Afghanistan use the Solar Hijri calendar, one of the most accurate calendar systems ever devised. It’s a solar calendar that begins at the vernal equinox (Nowruz, the Persian New Year, around March 20-21). The first six months have 31 days, the next five have 30, and the last has 29 (30 in leap years).

The calendar epoch is the same as the Islamic Hijri calendar (622 CE), but because it follows the solar year, dates don’t drift through the seasons. Its leap year system is based on astronomical observations, making it exceptionally precise.

The Buddhist Calendar

Used in Southeast Asian countries including Thailand, Myanmar, Sri Lanka, Cambodia, and Laos, the Buddhist calendar is a lunisolar system. Thailand’s variant is the most widely known — the Thai solar calendar uses the same months as the Gregorian calendar but counts years from the death of the Buddha, placing the current era around 2569 BE (Buddhist Era).

Living with Multiple Calendars

In our interconnected world, many people routinely navigate multiple calendar systems. A business meeting might be scheduled using the Gregorian calendar, while a family celebration follows the lunar calendar. Modern technology helps bridge these systems — your phone can often display dates in multiple calendars simultaneously.

The existence of so many calendar systems is a testament to humanity’s universal fascination with tracking time and the diverse ways different cultures have solved the same fundamental challenge: organizing the cycles of the sun, moon, and seasons into a practical system for daily life.