Lunar calendar

From ArticleWorld

A lunar calendar is a dating system that uses lunar cycles and phases to measure time instead of the sun. However, most lunar calendars are actually lunisolar, and use solar as well as lunar cycles to measure time.

Calendars

The Muslim calendar is commonly recognized as one of the few entirely lunar calendars in use today. This calendar has little or no practical use in everyday life, so it is confined to religious use in the Muslim community.

The Hindu, Hebrew and Chinese lunar calendars are actually lunisolar, though they are commonly referred to as “lunar calendars.” Thus, the Chinese new year is often called the “Lunar new year.”

Because all of these calendars are at least partially lunar, the holidays on these calendars do not fall on the same dates in consecutive solar years. Thus, holy days like the Muslim Ramadan and the Jewish Hanukkah fall on different days and even different months every Gregorian solar calendar year.

Measurement of cycles

In all lunar calendars the first day of each month depends on the phases of the moon. Some calendars begin their month at the start of the new or dark moon while others do not start the month until the first new crescent moon is observed.

The actual time it takes for the moon to go through a complete phase cannot be perfectly subdivided by any full number of days. It takes a little more than 29.5 days for this phase to occur, and, thus, over time, lunar calendars will begin to slip and become more and more inaccurate over time. Increasingly complex fractions and dividing schemes have been created to make lunar calendars more accurate.