Months

A month (plural: months) is a unit of time that forms part of the year. Historically, it was based on the lunar cycle—the period required for the moon to complete its changes in appearance as seen from Earth. Consequently, in many languages the word for month is connected to the word for moon; in Somali, the word "bil" belongs to the category of words specifically denoting time.

The lunar month as measured by appearance (from new moon to new moon) is approximately 29 and a half days. Because this is not a whole number, different calendar systems use months of 29 or 30 days, or include intercalary months not tied to the moon, so that twelve months align with the solar year.

Types of calendar systems

Calendar systems are divided into three major types. Lunar calendars (such as the Islamic calendar) have months that directly follow the moon's phases, and the year is shorter than the solar year by roughly eleven days, causing months to rotate through the seasons. Solar calendars (such as the Gregorian calendar used internationally) have months that are merely divisions of the year independent of the moon. Lunisolar calendars (such as the Hebrew calendar) insert an extra month in certain years to keep months aligned with the seasons.

The international calendar

The Gregorian calendar, which is now widely used in international administration and commerce, has twelve months: January, February, March, April, May, June, July, August, September, October, November, and December. These months have 30 or 31 days, except for February, which has 28 days, or 29 in leap years.

Islamic months

The Hijri calendar consists of twelve lunar months: Muharram, Safar, Rabi' al-awwal, Rabi' al-thani, Jumada al-awwal, Jumada al-thani, Rajab, Sha'ban, Ramadan, Shawwal, Dhu al-Qi'dah, and Dhu al-Hijjah. Each month begins when the new moon is sighted or calculated. Several of these months carry religious significance—for example, Ramadan is the month of fasting, and Dhu al-Hijjah is when the pilgrimage takes place.

Somali usage

Somali practice has employed both systems: the names of Islamic months for religious observances and celebrations connected to them, and the names of international months for government, education, and commerce. There also exists a seasonal system used by pastoralists and herders to mark rainfall and pasture conditions, which does not directly follow the named months of any written calendar.