Introduction to Lunar and Solar Calendars

In order to construct the accurate chronologies of several important regions in the world, one must fully understand the calendars used by the Israelites, ancient Babylonians, Persians, and Chinese. In the ancient world, there were essentially three types of calendars: lunar, solar, and lunisolar.

Calendars based solely on the Moon's motion are called lunar calendars. The time it takes the Moon to orbit the Earth is about 29.53 days on average. Therefore, some months in the lunar calendar have 29 days and other months have 30 days. There are twelve lunar months and about 354/355 days in each lunar year. The pure lunar calendar that is based solely on the Moon's motion has been used in the Islamic countries of the Middle East.

Calendars based only on the Sun's motion (relative to the Earth) are called solar calendars. One type of solar calendar was recorded in the book of Enoch and used in the first and second century BC by Essenes, one of the Jewish sects. The normal year in Enoch's solar calendar consists of eight 30-day months and four 31-day months (the third, sixth, ninth, and twelfth month), making a total of 364 days and 52 weeks. Another type of solar calendar called the Julian calendar was proposed by Julius Caesar in 46 BC. The Julian calendar was predominantly used in the Roman world but was gradually replaced by the Gregorian calendar after 1582 AD.

A lunisolar calendar is a calendar whose dates mark both the moon phases and the seasons of the solar year. The normal years in the lunisolar calendar consist of 12 months and each month has 29 or 30 days. Every second or third year is called embolismic year in which a leap month is added to synchronize the lunar year with the solar year. The Hebrew, Chinese, Korean, and Babylonian calendars are all lunisolar. The variations of these lunisolar calendars lie with the differences in the definitions of the first day of a month and the first month of a year, and in the ways of intercalating the leap month. In the Hebrew, Chinese, and Korean calendars, the first day of a month corresponds to a day when the moon is hidden (dark moon). Within this criterion, the full moon mostly falls on the 15^th day of a month. Consistently, the recorded lunar eclipses (occurring at the full moon) mostly took place on the 15^th day. In contrast, the first day of a month in the Babylonian calendar corresponds to the day when a new crescent is seen in the western sky after sunset. Within this criterion, the full moon mostly falls on the 14^th day of a month. That is why the lunar eclipses recorded by the Babylonians occurred mostly on the 14^th day.

Remarkably, the Chinese lunisolar calendar (Xia calendar) is quite similar to the Hebrew one. The major difference is that the Chinese New Year starts one month or two months earlier than the Hebrew New Year. According to the instruction of Yehowah, the God of Abraham, Isaac, and Jacob, the first month of a year corresponds to the month in which the Vernal (Spring) Equinox falls. The Chinese Mid-Autumn Festival is celebrated on the 15^th day of the 8^th month of the lunisolar calendar with a full moon at night. This day mostly corresponds to the 15^th day of the 7^th month in the Hebrew lunisolar calendar, which is the first day of the Feast of Tabernacles. The original Mid-Autumn Festival was to celebrate the harvest and to give thanks to the heavenly God, which is similar to the Feast of Tabernacles. Later on, this festival developed into moon worship.

We will discuss the Hebrew lunisolar calendar in detail in Chapter 2, the Babylonian lunisolar calendar in Chapter 3, Enoch's solar calendar in Chapter 4, and the Chinese lunisolar calendar in Chapter 5. Understanding these calendars is essential to both the construction of the accurate Biblical chronology and to deciphering the Biblical numerical prophecies. Readers could initially skip this part (Part I) and directly jump to Part III if they do not have a strong background in science and history.