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Lunar calendar

A lunar calendar is based on the changes of the cycles of the Moon’s phases (synodic months) – unlike solar calendars, whose yearly cycles are based directly on the solar year. The most common calendar, the Gregorian calendar, is based on the solar calendar system, which evolved out of the lunar system.

A purely lunar calendar is also different from a lunisolar calendar, whose lunar month cycles are aligned through a certain process of complementation. The day of the beginning of a month differs based on the type of the calendar. In some calendars, it is based on the new moon, full moon, or crescent, while in others it is based on more complicated calculations.


A full cycle

As each full lunar cycle (lunation) lasts for about 29.5 days (29 days, 12 hours, 44 minutes and 3 seconds, i.e. 29.530588 days), months in lunar calendars have either 29 or 30 days. And because a period of twelve such cycles – the lunar year – lasts approximately 354 days, 8 hours, 48 minutes and 34 seconds (354.367056 days), purely lunar calendars lose about 11 days per year compared to the Gregorian calendar. In purely lunar calendars, like the Islamic calendar, the missing part causes lunar months to pass through all the periods of the Gregorian year during a 33-year long cycle of lunar years.

Although the Gregorian calendar is the one commonly used and set by law in most countries, traditional lunar and lunisolar calendars are still used in the Old World for determining religious and state holidays.

The length of each lunar cycle slightly deviates from its average value. Furthermore, observations are based on uncertain parameters and weather. To cope with this uncertainty, there have been efforts to set rigid arithmetic rules for determining the beginning of each calendar month.


The 2018 Cannapedia calendar contains valuable information on the lunar cycle and its practical use, including this time its relation to fruit trees and other crops, as well as human well-being. Available in the Canatura.com e-shop.

Lunární kalendář