The Hebrew Calendar (Part 2)

In part 1 of our series on the Hebrew Calendar we saw how the Hebrew calendar has a different number of days in a year than the Gregorian calendar. The twelve month Hebrew year has 354 days, eleven or twelve days less than the Gregorian calendar. In seven years out of a nineteen year cycle, a thirteenth month is added to make up for the lost days. In the third, sixth, eighth, eleventh, fourteenth, seventeenth and nineteen years out of a nineteen year cycle there are thirteen months.

The Hebrew calendar months alternate between 29 and 30 days:

Month     Number of Days

Nisan              30
Iyar                 29
Sivan               30
Tamuz             29
Av                   30
Elul                  29
Tishri               30
Heshvon          29
Kislev              30
Tevet               29
Shevat             30
Adar             29/30
Adar II             29

In a twelve month year, the month of Adar has twenty-nine days. In a leap-year (thirteen month year), Adar has thirty days and Adar II (the added thirteenth month) has 29. So the twelfth month, Adar can have either 29 or 30 days depending on if the year is a leap-year or not. With that reasoning the Hebrew year can have either 354 or 384 days.

Now we need to begin to see if we can see how close we can come to reconciling the number of days between the two calendars. Although some have had loosely said the number of days matches up over nineteen years, that is not exactly the case, there is a slight difference. Let's see how close they come.

• A lunar month is actually 29 days, 12 hours, 44 minutes and 2.8 seconds. This is how long it takes the moon to circle the earth and is what lunar months are based on. In decimal format this is 29.530587963 days.
• Twelve lunar months make up 354.37 days. Twelve months on the Gregorian calendar are 365.2425 days.
• The number of days in the Gregorian calendar over nineteen year is:
19 (years) x 365.2425 (days per year) = 6,939.61 day
• The number of days in a twelve-month lunar calendar over nineteen years is:
19 (years) x 29.530588 (days per month) x 12 (months) = 6,732.97 days
• In the modified lunar (lunisolar) calendar, the Jews insert a thirteenth month (Adar II) in seven years out of every nineteen year cycle. The additional number of days accounted for by this thirteenth month is:
7 (years with thirteen months) x (29.53088 (days per month) = 206.71 days.
• When we add the number of days in nineteen, twelve-month lunar calendar years to the days added during the seven years when there are thirteen months we have:
6,732.97 + 206.71 = 6,939.68 days

The Gregorian and modified lunar calendars thus reconcile to within .07 of a day over nineteen years.
6,939.68 – 6,939.71 = .07


Summary: Number of Days over Nineteen Years
Gregorian (Solar) Calendar
Days per year = 365.2425
Days in 19 years = 6,939.61

Hebrew (Lunisolar) Calendar
Days per month = 29.530588
Days per year (12-month year) = 354.367056
Days per year (13-month year) = 383.897644
Total days in 12 12-month years = 12 x 354.37 = 4,252.40
Total days in 7 13-month years = 7 x 383.90 = 2,687.28
Total days in 19 years = 6,939.68

Difference over 19 years = .07 day


Part 3 of this series will discuss the significance of .07 of a day plus a couple more tid-bits of information.

For more information about the roots of Christianity check out www.feelingoutstanding.com/ID.html.

Tom Thorne

The Hebrew Calendar, Part 1

The Hebrew Calendar (Part 1)

The Gregorian calendar is the method of reckoning dates used by most of the world. It was sponsored by Pope Gregory XIII n 1582 as a corrected version of the Julian calendar. It is a solar-based calendar in which dates represent the position of the earth in its revolution around the sun.

The Hebrew/Jewish calendar is quite unlike the Gregorian or the Julian calendar. It is a modified lunar-based calendar—that is, based on cycles of the moon phase. It is also adjusted by adding intercalary months (that is, a thirteenth month in certain years) to bring the lunar cycles into synchronization with the solar year.

Trying to understand the Holy Day dates on the Gregorian calendar can be quite challenging. For example, the Feast of Trumpets (Rosh Hashanah) falls on the Hebrew calendar date of Tishri 1. One may wonder why in some years Tishri 1 may fall early in September, while in others it may be as late as October. Having a basic understanding of the modified lunar calendar used by the Jewish people provides us with the answers. In this chapter, I will demonstrate how to reconcile the disparities between the numbers of days in the Jewish and Gregorian calendars.

The calculations used may appear to be a little bit intimidating, with long decimal places and many steps, but they are really very straightforward and simple. Gaining knowledge into the Jewish calendar will greatly assist in understanding why the Holy Days do not occur at the same time on our calendar every year. In addition, learning a completely different way to reckon months and years can be quite interesting.

The major points to note are that the lunar calendar has 29.53 days in a month. Twelve months are equal to approximately 354 days, 11 or 12 days less than twelve months in the Gregorian calendar. To make up for this difference, the Jewish calendar adds a thirteenth month in seven years out of every nineteen, so that the “modified lunar” (lunisolar) calendar and the Gregorian calendar come into almost exact alignment every nineteen years. The table below demonstrates the number of months in a year for the two calendars, representing the current nineteen-year cycle.

Hebrew                       Gregorian
Year   # of Months      # of Months    Year
5758           12                  12             1997
5759           12                  12             1998
5760           13                  12             1999
5761           12                  12             2000
5762           12                  12             2001

5763           13                  12             2002

5764           12                  12             2003

5765           13                  12             2004
5766           12                  12             2005
5767           12                  12             2006

5768           13                  12             2007

5769           12                  12             2008

5770           12                  12             2009

5771           13                  12             2010

5772           12                  12             2011

5773           12                  12             2012

5774           13                  12             2013

5775           12                  12             2014

5776           13                  12             2015

In part II in this series we will determine how well the days between two common calendars can be reconciled.