Calendar Drift Describes Early Rosh Hashanah

Asteroids, ice ages, and miserable cousins come and go every now and then. But never again will Rosh Hashanah fall as early as it does this year on September 5.

Forget about the Mayan apocalypse of 2012. Even anti-Israel astrophysicist, Stephen Hawking, must be going 'meshugah' over this year's Jewish calendar phenomenon.

Art collectors of Art Kabinett social media network are always interested in obscure mathematical complexities which possess artistic appeal in their own right.

Based upon the modern Gregorian solar calendar, the earliest date on which Rosh Hashanah can fall is September 5, as happened in 1899 and will happen again this year, 2013. By Biblical law, Rosh Hashanah must occur 163 solar days after the first day of Passover.

The latest date that Rosh Hashanah can occur relative to the Gregorian dates is October 5, as happened in 1967 and will happen again in 2043.

After 2089, the differences between the Hebrew calendar and the Gregorian calendar will result in Rosh Hashanah falling no earlier than September 6. Thus, no human will ever again experience Rosh Hashanah this early.

Two problems affect the situation – the discrepancy between the lunar and solar calendars, and the discrepancy between the Jewish and Gregorian cycle.

To ensure that the Passover holiday -- governed by the lunar calendar --falls in the spring, which is determined by the solar calendar, there is a corrective mechanism which inserts an extra month into the year seven times in every nineteen-year cycle. The extra month creates a "shanah m’ubberet", a “leap or literally “pregnant”) year.

The second discrepancy entails an annual difference of a couple of hours between the Jewish lunar and Gregorian solar cycles.

The solar calendar is 365.25 days in length. The lunar calendar is approximately 354 days in length. In order to almost even out the lunar and solar years, Jews add seven leap years in every 19 years. In each of those leap years, a month of 29 or 30 days is added to the calendar.

Unfortunately, the leap years do not totally equalize the calendars. There is a slow drift going on in the Jewish calendar:

235 lunar months add up to 6,939 days 16 hours 595 parts. (In Jewish calendar math, "parts" are the basic subdivisions of an hour, instead of minutes and seconds. There are 1,080 parts in an hour, so 595 parts is about 33 minutes.)

In the Gregorian calendar, 19 solar years (on average) are 6,939 days 14 hours 626 parts. That's about a 2-hour difference. So the Jewish holidays (on average) shift about 2 hours later during each 19-year cycle, which adds up to a full day every 231 years

For those of you still reading, you can see that the lunar calendar is drifting.

However, because of the aforementioned calendar drift going on for the present couple of centuries. The earliest Rosh Hashanah used to be Sept. 4 (which means Purim on Feb. 23, and so on for the rest of the holidays), but that happened for the last time in 1766. The last Sept. 5 Rosh Hashanah (until we loop all the way around, of course) will be in 2089; after that, the earliest will be Sept. 6.

We hope that helps you understand the early start of this year's Jewish New Year. But to put it simply it is to keep the calendars as aligned as possible.

The result is that the 1st day of the Jewish month of Tishri -- the Jewish calendar date of Rosh Hashanah -- becomes very slightly later each year, but no-one notices the difference from one year to the next and it will take 1900 years for the slight differences to add up to a week.

If you truly comprehend this explanation, you are entitled to another Bar Mitzvah! L'Shana Tova (Happy Jewish New Year) from all your art collector friends.