In nearly all societies, the calendar is usually subdivided into months, weeks, and days, with specific days or dates noting certain cultural and religious holidays, as well as celestial events. In Western societies, our year is based on the Gregorian calendar. Officially the standard for most of the world, it was introduced by and named for Pope Gregory XIII in 1582. This replaced the Julian calendar, which in turn replaced the Roman calendar. The Gregorian and Julian calendars are solar, as they’re based on the time it takes for the Sun to return to the same point in the sky as observed on Earth. On a solar or tropical calendar, each solar day is assigned an individual date. If a “solar year” is a thing, then it stands that a lunar year must also be a thing. While Christian timelines are based on solar years, other faiths and cultures (like the Islamic calendar) are based on lunar and lunisolar calendars, which we’ll explore here.
Comparing Calendar Types
A solar year is approximately 365.25 days. A lunar year is based on 12 lunar months, wherein each month is based on the period it takes the moon to go through each phase. A lunar month is approximately 29.5 days, making a lunar year only 354 days. This means that every 33 years, solar time and lunar time are off by approximately 365 days! The Islamic or Hijri calendar is lunar.
A lunisolar calendar combines elements of both solar and lunar types. While months are divided according to lunar phases, the year includes adjustments so that the overall length coincides with a solar year. Jewish, Buddhist, and Hindu religious calendars are lunisolar. The Chinese calendar is also based on a lunisolar year.
Examining the Islamic and Hijri Calendar
In most Muslim countries, the Hijri calendar is used to date certain religious events. Adherents use this calendar to mark the observance of certain holy days. Ramadan is a month of fasting that commemorates the Islamic prophet Muhammad’s first revelation. It occurs in the ninth month of the Hijri calendar. Because the Islamic year is shorter than the Gregorian year by ten to twelve days, Ramadan occurs ten to twelve days earlier each year. This has the net effect of Ramadan cycling through every part of the Gregorian year every 33 years. Another effect of these annual differences means that Muslims have two ages, one based on the Hijri calendar, and another based on the Gregorian calendar. Whereas the Gregorian calendar is in the year 2023, the Islamic calendar is in the year 1445.
Starting the Year on Time
If different calendars weren’t confusing enough, consider also that different religions and cultures have different dates for the New Year. In most Christian denominations, whether based on the Gregorian or Julian calendars, the New Year starts on January 1. Consider these New Year (Gregorian) dates in other faiths and cultures:
- Chinese: Also known as the Lunar New Year, this occurs on January 22.
- Hindu: Based on a lunisolar calendar, the Hindu New Year is observed on April 1.
- Islam: Muslims mark the start of each year on July 30.
- Jewish: Rosh Hashanah marks the beginning of the Jewish lunisolar calendar. The date varies based on Jewish months.
- Persian: Although the Persians use a solar calendar, they acknowledge the new year on March 21.
While many of the world’s faiths seem to be based on a set of tenets, time is an important factor. Various calendars are used by different religions to acknowledge holy days and years. The next time you meet someone who practices a different faith, consider inquiring about the type of year used and, if appropriate, that person’s solar, lunar, or lunisolar age.