Calendar

A calendar (also called kalandar or maalintiris) is a system for organizing time, particularly days, weeks, months, and years. Calendar systems are based on the motions of the heavens: Earth's orbit around the sun, the moon's orbit around Earth, and the alternation of night and day.

Calendars serve agricultural planning, calculation of religious observances, historical record-keeping, and state administration. Each society has its own method of defining the start of the year and counting years.

Major types

Three main types are distinguished. The solar calendar follows the yearly orbit of the sun, so seasons occur at fixed times. The lunar calendar is based on the moon's months, making its year shorter than the solar year, which causes the months to shift relative to the seasons. The lunisolar calendar uses lunar months but periodically adds an extra month to stay aligned with the sun.

The Gregorian calendar

The Gregorian calendar is today used worldwide for commerce and administration. It comes from a reform of the Julian calendar of Rome. The year has 365 days, and one extra day (leap year) is added every four years, with special rules for century years to minimize error.

The Hijri calendar

The Hijri calendar is a lunar calendar with twelve months, and its year is approximately 354 days. For this reason, Islamic observances such as Ramadan advance earlier each year when compared to the solar calendar. It counts from the Hijra of the Prophet Muhammad from Mecca to Medina. Among Somali communities, both calendars are used together: the Hijri calendar governs religious matters, and the Gregorian for administration.

Cultural reckoning of seasons

Alongside written calendars, pastoral and farming communities use seasonal reckoning based on rainfall, winds, and star positions. For example, Somali seasons—Gu, Xagaa, Dayr, and Jiilaal—divide the year into four periods marked by rainfall and drought.