Happy Jewish New Year 5780 everybody; may it be a sweet and prosperous one. But that’s not what this article is about.
When we think of a calendar, most people think of the Gregorian calendar. You know the one that’s 365.25 days per year and all western countries use it. That one. Remember though that every four years that
.25 turns into a full day we now call a leap year.
However, not everyone realizes that there are more types of calendars, including ones that don’t even follow the sun. But the
Gregorian calendar is the dominant calendar created by dominant social groups.
The Hebrew calendar was created by a critical narrative. The issue is that the calendar is much more complicated because it has to align the solar calendar (365 days, 5 hours, 48 minutes and 46-seconds) and the lunar calendar which is 12 months of 29 days, 12 hours, 44 minutes and 3 seconds. This is an issue because the lunar year by this measure is 12 days shorter than the solar year.Now you might be thinking, how is it that the two calendars get aligned when the lunar calendar is 12 days shorter and also what is the math behind it? The Hebrew calendar is based on the nineteen-year cycle shown here. However, the cycle starts over every nineteen years, but the actual leap years are on a schedule within this system in a numerical pattern. This is how the Gregorian and Hebrew calendar stay aligned. The Jewish leap year pattern is to add an extra month every 3,6,8,11,14,17, and 19 years. The reason they add an extra month in every two to three years is that there are 2.6 extra days in the Gregorian calendar. The Jewish calendar needs to align with the Gregorian (solar) calendar because Jewish Passover needs to always occur in the spring in the Northern Hemisphere. Therefore, the Jewish calendar adds in an extra 29 day month every two to three years (with more three year gaps because 2.6 is closer to three than two) to make up for the fact that the normal Jewish year has fewer days in it. This hopefully gives you a greater idea of other calendars that are used by other cultures and religions besides the Gregorian calendar.