A Short Comparison of the Rabbinical and Karaite Hebrew Calendars

Figure 1: Chloe the Wiener Dog has cotton applied to her ears to treat a brain hemorrhage brought on by trying to calculate the date of the Rapture.

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The purpose of this study is to briefly compare the Rabbinical and Karaite Hebrew calendars while resulting in minimal damage to the reader’s brain. If, while reading, blood begins to flow from your ears, discontinue reading and apply cotton as in Figure 1. If bleeding is profuse, see a professional immediately to see whether you have popped a brain gasket.

The difference between the two Hebrew calendars boils down to how they answer these two questions:

1. How do we determine the beginning of a new year?

2. How do we determine the beginning of a new month?

Once you understand those two questions, and how each calendar answers them, you will understand the meat and potatoes of both calendars.

The Gregorian Calendar

Let’s begin by reviewing the Gregorian calendar, which is the one we are all familiar with. The Gregorian calendar is entirely concerned with the passage of the Earth around the Sun. Since it takes about 365 1/4 days for the Earth to go around the Sun, most Gregorian years are 365 days long. However, those 1/4 days do add up after a time, so an extra day is added, usually every 4 years, and we a year with 366 days. The year 2010 has 365 days, as will 2011. The year 2012, if we get through it without being deluged by really bad movies, will have 366 days. This extra day every few years keeps the Gregorian year in sync with the seasons. Otherwise, after several centuries, December 25 would fall in the middle of summer, and that, apparently, would be bad. At least in the northern hemisphere.

Lunar Calendars

Both the rabbinical and karaite calendars are lunar calendars. The months are based on the phases of the moon. It takes about 29 or 30 days for the moon to go around the earth. (The period of time varies throughout the year.) The average lunar month is 29 1/2 days, so 12 lunar months — one lunar year — is 354 days long. That’s 11 days less than a solar year, so the lunar year quickly becomes out of phase with the solar year. This presents a problem if you want to keep your spring festivals in the spring and your autumn festivals in the autumn. The Islamic calendar is completely lunar, so the Islamic festivals roam through the seasons. However the Hebrew festivals have an agricultural element, at least historically. During the Passover season, the priest used to present the first sheaves of the barley harvest to God in the Temple. The barley harvest is the spring, so a barley festival in the winter just won’t do.

Rabbinical vs. Karaite Solutions

Remember that the lunar year is 354 days long while the solar year is 365 days long. So each year, Passover comes 11 days earlier than the year before. After 3 years, Passover — and the barley festival — would be 33 days earlier. The solution for both the Rabbinical and Karaite calendars is to add a 13th month now and then to eat up those 33 days.

Now we are ready to look at the first distinction between the two calendars. Remember the first question:

1. How do we determine the beginning of a new year?

Both calendars keep their years in sync with the seasons by adding an extra month just before Passover. So, as Passover drifts earlier, in pops a 13th month to whack it back into place. The calendars differ based on how they determine when to add that month. The Rabbinical calendar follows a set routine based on a 19-year cycle.  In years 3, 6, 8, 11, 14, 17 and 19 of the cycle, a 13th month is added. This keeps the Hebrew calendar nicely in sync with the seasons. It also helps us to plan Passover picnics, because we know a year ahead of time — in fact, 100 years ahead of time — when Passover will be because we have all those 13th months planned out ahead of time.

The Karaite calendar, however, hearkens back to the agriculture era when the festivals were closely tied to the harvests. Therefore, each year, toward the end of the 12th Hebrew month, there are people who actually tromp through the grain fields in Israel. They investigate the maturity of the barley they find growing and if it is ripe, they judge that spring has arrived, and that Passover can be celebrated the following month. If the barley is not ripe, they report that Passover will be delayed, and Karaites around the world — as well as their followers — add an extra month to their calendars. The result for everyone is that Passover stays in the spring, although you have some people in some years celebrating a month later than others.

The second question, you will recall, has to do with determining the beginning of each month:

2. How do we determine the beginning of a new month?

The solution, for both the Rabbinical and Karaite calendars is the calculate the months based on knowledge of the position of the moon in relation to the sun. The first of the month in each case corresponds to the beginning of the lunar cycle, or new moon. The difference for each is how they define the new moon. In the Rabbinical month, the new moon corresponds to that time when the moon and the sun are together in the sky so that you can’t actually see the moon. In the Karaite month, the new moon is a couple of  days later, when the crescent moon can be seen in the west, just above the sun after it sets. The Karaites calculate this astronomical event ahead of time, so like their Rabbinical friends, know ahead of time when their months will begin. There are occasions, however, when the Karaite calculations are inconclusive, and the new month needs to be confirmed by a sighting in Israel. Some Messianics prefer to confirm all new months with a sighting. The result is that the Karaites usually celebrate their holidays a day or two after the corresponding Rabbinical holiday.

The following summarizes the differences between the two calendars:

13th Month:

Rabbinical:  Calculated ahead of time

Karaite: Based on the observation of barley

New Month:             

Rabbinical: Calculated ahead of time, when moon is not visible

Karaite: Calculated, sometimes confirmed by observation of crescent moon

One final difference worth mentioning pertains the the celebration of Shavuot. Since the date of Shavuot is based on “the day after the Sabbath” of Passover week, there is some ambiguity. The Rabbinical calendar takes “Sabbath” to refer to the first day of Passover, which is a high Sabbath. The Karaites take this to mean the weekly Sabbath during Passover week. The result is two separate days for the celebration of Shavuot.


6 thoughts on “A Short Comparison of the Rabbinical and Karaite Hebrew Calendars

  1. Leviticus 23 describes “festivals, the holy occasions to be observed at the proper time each year.” First comes the Lord’s Passover, which begins at twilight on its appointed day in early spring. How is that day determined? And which calendar is used in Leviticus?

  2. I really enjoyed reading this comparison of simplicity! Just what I needed to clear some things up! I have been looking at different caledars and trying to be sure I am on the right one. This helped me be more at ease about all that!


  3. The days of unleavened bread in Lev 23 —- 15th thru 21st are not Passover days as Jews call them. Passover is the 14th and the literal Hebrew is “between the evenings”. All of God’s days are between evenings (sunsets). The modern Jewish interpretations of this are idiomatic and not the original Hebrew. All the rites of the Passover were to fall on the 14th day and between the sunsets per Numbers 9.

  4. I did some comparison using hebcal and http://www.calendar-365.com/moon/moon-phases.html comparing the beginning of the Hebrew months at hebal.com which uses the rabbinic calendar to the new moons for the US, and the rabbinical calendar is accurate within a day to the US new moons. For instance, a Karaite calendar I found at http://www.karaite-korner.org/holiday_dates.shtml says the new moon was sighted on October 6th, For the US the new moon should have been October 4th, and the rabbinic calendar at hebal has Rosh Chodesh Cheshvan on October 4th.

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