A lunar calendar is simply a calendar that is based on the cycles of the moon. Such calendars have been used since antiquity — archaeologists have found evidence of lunar calendars that date back as far as 32,000 years ago. Some artifacts from the Ice Age, about 25000 and 10000 BCE, include sticks, reindeer bones, and mammoth tusks with carved notches and gouged holes in them. Many academic scholars believe that these marks depict the days between moon phases.
The Mayan Calendar was a lunar calendar system based on the agriculture requirements of living in a rain forest. The Mayans invented numerous calendar systems, but the most important one was the sacred tzolkin. This calendar was made up of 260 days and had two repeating cycles. One cycle consisted of 13 numbered days and the other cycle was made up of 20 named days.
The Babylonian calendar was another lunar calendar system. This calendar consisted of 12 months that alternated between being 29 days and 30 days long. Months with 29 days were called "hollow," while those with 30 days were called "full." The Babylonians eventually switched to the Egyptian calendar system, which was 12 months and 30 days long. This calendar was used for over 3000 years, not falling out of favor until about 238 BCE.
The Chinese originally used a lunar calendar system to determine the best times to plant, harvest, and hold their many religious festivals. Though a majority of modern Chinese citizens use the Western solar calendar for the more practical matters of their everyday lives, the old lunar calendar is still used to determine the dates of holidays and festival occasions. The Chinese people have long accepted this coexistence of two different calendar systems.
The only purely lunar calendar widely used today is the Islamic calendar, called the Hijri calendar. The years always have 12 lunar months. Because of the varying length of these lunar months, this calendar can’t be linked to the seasons. While the Hijri calendar is the official calendar in countries around the Gulf, including Saudi Arabia, other Muslim countries only use the Islamic calendar for religions purposes and use the Gregorian calendar for civil purposes.