Al-Qaidah Al-Qamariah,

The lunar year is defined as the time it takes for the moon to complete 12 cycles, with each cycle corresponding to one lunar month. Since a lunar month is approximately 29½ days long, the months in the lunar calendar commonly alternate between 29 and 30 days. This results in a total of 12 lunar cycles, making the lunar year approximately 354 days, 8 hours, 48 minutes, and 34 seconds (or 354.36707 days). A pure lunar year is 11 to 12 days shorter than the solar year.

While the Gregorian calendar is widely used and is used as the official calendar in most countries, traditional lunar and lunisolar calendars continue to be employed worldwide for determining religious worship, observances, holidays, and national festivals. In Lebanon, the lunar phase that determines the start of the months is based on detailed calculations that Muslim and Christian farmers do to schedule their agricultural activities, including planting and harvesting.

The lunar phase calculation process is essential for tracking the moon’s cycles and identifying days when the moon is full or empty. This process compensates for the approximately 11-day difference between the lunar and solar years, with the solar year being longer. ​Moon phases refer to the parts of the moon illuminated by the sun, as seen from earth. In the night sky, the moon sometimes appears round, sometimes like a crescent, and sometimes it is simply not visible. The origin of this phenomenon comes from the position of the moon between the sun and the earth. Indeed, just like the earth, part of the moon is always illuminated by the sun while the other part is in darkness. Since the moon changes position slightly each day in relation to the sun and the earth, this means that the perception of the illuminated part of the moon is not the same. Thus, we have the impression that the moon changes shape over time, which we call phases of the moon. A complete cycle of the phases of the moon is called a lunation.

This rule makes it possible to determine the phases of growth and waning of the moon and to divide the lunar month into 5 days full/5days empty, 4 days full/4days empty, 3days full/3days empty, 2days full and 2days empty 1 day full and 1 day empty.

This calculation helps farmers decide the best days for various agricultural tasks. Cultivation, plowing, planting, and firewood cutting are typically favored during the full moon. Harvesting crops like onions and garlic is preferably done when the moon is not visible.

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