Hebrew Calendar Science and Myths

Hebrew Calendar Science and Myths September 16

by Remy Landau =================================

When a small number of consecutive Rosh Hashannah's are mapped onto either the Gregorian or the Julian calendars, all of the leap years normally appear to begin no later than a particular Gregorian or Julian date, and all of the 12 month years normally appear to begin no earlier than that same Gregorian or Julian date.

Presently, and for about the next 120 years, no 13 month Hebrew year can begin any later than the Gregorian date September 16, and no 12 month Hebrew year can begin any earlier than that date.

For purposes of discussion, this date will be referred to as a Separation Date. It has the property that no 13 month Hebrew year can start after this date, and no 12 month Hebrew year can start before this date.

However, there may be some rare exceptions in which either type of year could begin a few days on either side of this limiting date.

As shown in Separation Dates, this civilian date keeps apace with The Rosh Hashannah Drift.

September 16 first became a Separation Date on Sat 16 Sep 1871g (5632H) and will remain in effect until Sat 17 Sep 2118g (5879H).

Its total duration as a Separation Date is 247 years (13 * 19 years).

A civilian calendar date can be a Separation Date for as long as 399 years. For example,
23 Aug -3753g (8H) remained as the first Separation Date until 24 Aug -3354g (407H).

Longer durations are possible for the Separation Date

Some civilian dates are occasionally bypassed in that role.

Rosh Hashannah progresses through all of the days of the Gregorian calendar at an average rate of about once in every 84,507 years.

Each time that Rosh Hashannah first coincides with a new Gregorian date, the new Hebrew year is a 12 month year.

Normally, that new Gregorian date also becomes the latest possible date for the start of
Rosh Hashannah.

The Rosh Hashannah Drift causes that Gregorian date to become a relatively earlier date as newer and later dates begin to host Rosh Hashannah.

As the Gregorian date becomes an earlier and earlier date for Rosh Hashannah, it begins to host the start of Hebrew leap years (ie, 13 months years). The first time that a Gregorian date hosts a Hebrew leap year normally marks the time that it becomes a Separation Date.

Sat 17 Sep 2118g (5879H) will be the first time that a Hebrew leap year begins on that Gregorian date. The event will therefore mark September 17 as the new Separation Date.

From that time forward, until a subsequent Gregorian date begins to host the start of Hebrew leap years, all Hebrew years that start before the date will be leap years, and all Hebrew years that begin after that date will be 12 month years.

On September 16, the year can be either leap or non-leap. However, after 5849H (2088g) all Hebrew years beginning on or prior to September 16 will be leap years.

The table below shows, ordered by day and month, the Gregorian dates for Rosh Hashannah between the years 5632H (1871g) and 5879H (2118g) .

The table also indicates the length of the Hebrew year started on each of these Gregorian dates.

All of the dates prior to September 16 show the start only of Hebrew leap years, while all of the dates subsequent to September 16 show the start only of 12 month Hebrew years.

The year 5879H (2118g) marks the start of September 17 as the new Separation Date.

**The September 16 Separation**
1871g (5632H) To 2118g (5879H)
Gregorian Date	H Year	Length
Tue 5 Sep 1899g	5660H	384
Thu 5 Sep 2013g	5774H	385
Mon 5 Sep 2089g	5850H	385
Mon 6 Sep 1880g	5641H	383
Thu 6 Sep 1888g	5649H	385
Mon 6 Sep 1937g	5698H	385
Thu 6 Sep 1956g	5717H	385
Sat 6 Sep 1975g	5736H	385
Tue 6 Sep 1994g	5755H	384
Mon 6 Sep 2032g	5793H	383
Sat 6 Sep 2070g	5831H	383
Thu 6 Sep 2108g	5869H	385
Sat 7 Sep 1918g	5679H	383
Mon 7 Sep 1964g	5725H	385
Sat 7 Sep 2002g	5763H	385
Tue 7 Sep 2021g	5782H	384
Thu 7 Sep 2051g	5812H	383
Sat 7 Sep 2097g	5858H	385
Mon 7 Sep 2116g	5877H	385
Sat 8 Sep 1877g	5638H	385
Tue 8 Sep 1896g	5657H	384
Sat 8 Sep 1945g	5706H	383
Thu 8 Sep 1983g	5744H	385
Sat 8 Sep 2040g	5801H	383
Tue 8 Sep 2048g	5809H	384
Mon 8 Sep 2059g	5820H	383
Thu 8 Sep 2078g	5839H	383
Mon 9 Sep 1907g	5668H	383
Thu 9 Sep 1915g	5676H	385
Thu 9 Sep 1926g	5687H	383
Sat 9 Sep 1972g	5733H	383
Mon 9 Sep 1991g	5752H	385
Thu 9 Sep 2010g	5771H	385
Mon 9 Sep 2086g	5847H	383
Thu 10 Sep 1885g	5646H	385
Sat 10 Sep 1904g	5665H	385
Mon 10 Sep 1934g	5695H	383
Thu 10 Sep 1953g	5714H	383
Mon 10 Sep 2018g	5779H	385
Mon 10 Sep 2029g	5790H	383
Thu 10 Sep 2037g	5798H	385
Sat 10 Sep 2067g	5828H	383
Tue 10 Sep 2075g	5836H	384
Thu 10 Sep 2105g	5866H	385
Mon 11 Sep 1893g	5654H	385
Tue 11 Sep 1923g	5684H	384
Mon 11 Sep 1961g	5722H	383
Thu 11 Sep 1980g	5741H	383
Sat 11 Sep 1999g	5760H	385
Mon 11 Sep 2056g	5817H	383
Thu 11 Sep 2064g	5825H	385
Sat 11 Sep 2094g	5855H	383
Mon 11 Sep 2113g	5874H	385
Sat 12 Sep 1874g	5635H	383
Thu 12 Sep 1912g	5673H	385
Sat 12 Sep 1931g	5692H	385
Sat 12 Sep 1942g	5703H	383
Tue 12 Sep 1950g	5711H	384
Mon 12 Sep 1988g	5749H	383
Sat 12 Sep 2026g	5787H	385
Tue 12 Sep 2045g	5806H	384
Mon 13 Sep 1920g	5681H	385
Sat 13 Sep 1969g	5730H	383
Tue 13 Sep 1977g	5738H	384
Thu 13 Sep 2007g	5768H	383
Sat 13 Sep 2053g	5814H	385
Tue 13 Sep 2072g	5833H	384
Mon 13 Sep 2083g	5844H	383
Thu 13 Sep 2091g	5852H	385
Thu 14 Sep 1882g	5643H	383
Sat 14 Sep 1901g	5662H	383
Thu 14 Sep 1939g	5700H	385
Sat 14 Sep 1996g	5757H	383
Mon 14 Sep 2015g	5776H	385
Thu 14 Sep 2034g	5795H	385
Sat 14 Sep 2080g	5841H	385
Thu 14 Sep 2102g	5863H	383
Mon 15 Sep 1890g	5651H	383
Sat 15 Sep 1928g	5689H	385
Mon 15 Sep 1947g	5708H	385
Mon 15 Sep 1958g	5719H	383
Thu 15 Sep 1966g	5727H	385
Mon 15 Sep 2042g	5803H	385
Thu 15 Sep 2061g	5822H	385
Tue 15 Sep 2099g	5860H	384
Mon 15 Sep 2110g	5871H	383
Sat 16 Sep 1871g	5632H	383
Thu 16 Sep 1909g	5670H	383
Mon 16 Sep 1985g	5746H	383
Thu 16 Sep 1993g	5754H	355
Thu 16 Sep 2004g	5765H	383
Sat 16 Sep 2023g	5784H	383
Mon 16 Sep 2069g	5830H	355
Thu 16 Sep 2088g	5849H	354
Sat 17 Sep 1898g	5659H	353
Mon 17 Sep 1917g	5678H	355
Thu 17 Sep 1936g	5697H	354
Sat 17 Sep 1955g	5716H	355
Tue 17 Sep 1974g	5735H	354
Mon 17 Sep 2012g	5773H	353
Sat 17 Sep 2050g	5811H	355
Mon 17 Sep 2096g	5857H	355
Sat 17 Sep 2118g	5879H	383
Thu 18 Sep 1879g	5640H	354
Mon 18 Sep 1944g	5705H	355
Sat 18 Sep 1982g	5743H	355
Tue 18 Sep 2001g	5762H	354
Thu 18 Sep 2031g	5792H	354
Sat 18 Sep 2077g	5838H	355
Tue 19 Sep 1876g	5637H	354
Mon 19 Sep 1887g	5648H	353
Thu 19 Sep 1895g	5656H	355
Sat 19 Sep 1925g	5686H	355
Thu 19 Sep 1963g	5724H	354
Sat 19 Sep 2009g	5770H	355
Sat 19 Sep 2020g	5781H	353
Mon 19 Sep 2039g	5800H	355
Thu 19 Sep 2058g	5819H	354
Mon 19 Sep 2107g	5868H	353
Thu 19 Sep 2115g	5876H	354
Sat 20 Sep 1884g	5645H	355
Thu 20 Sep 1906g	5667H	354
Sat 20 Sep 1952g	5713H	355
Mon 20 Sep 1971g	5732H	355
Thu 20 Sep 1990g	5751H	354
Mon 20 Sep 2066g	5827H	355
Thu 20 Sep 2085g	5846H	354
Sat 20 Sep 2104g	5865H	355
Mon 21 Sep 1914g	5675H	353
Thu 21 Sep 1933g	5694H	354
Mon 21 Sep 1998g	5759H	355
Thu 21 Sep 2017g	5778H	354
Thu 21 Sep 2028g	5789H	354
Sat 21 Sep 2047g	5808H	353
Mon 21 Sep 2093g	5854H	355
Mon 22 Sep 1873g	5634H	355
Thu 22 Sep 1892g	5653H	354
Tue 22 Sep 1903g	5664H	354
Mon 22 Sep 1941g	5702H	355
Thu 22 Sep 1960g	5721H	354
Sat 22 Sep 1979g	5740H	355
Mon 22 Sep 2036g	5797H	353
Thu 22 Sep 2044g	5805H	355
Sat 22 Sep 2074g	5835H	353
Thu 22 Sep 2112g	5873H	354
Sat 23 Sep 1911g	5672H	355
Sat 23 Sep 1922g	5683H	353
Tue 23 Sep 1930g	5691H	354
Mon 23 Sep 1968g	5729H	355
Sat 23 Sep 2006g	5767H	355
Tue 23 Sep 2025g	5786H	354
Thu 23 Sep 2055g	5816H	354
Sat 24 Sep 1881g	5642H	355
Mon 24 Sep 1900g	5661H	355
Sat 24 Sep 1949g	5710H	353
Thu 24 Sep 1987g	5748H	354
Sat 24 Sep 2033g	5794H	355
Tue 24 Sep 2052g	5813H	354
Mon 24 Sep 2063g	5824H	353
Thu 24 Sep 2071g	5832H	355
Thu 24 Sep 2082g	5843H	354
Sat 24 Sep 2101g	5862H	355
Thu 25 Sep 1919g	5680H	354
Sat 25 Sep 1976g	5737H	353
Mon 25 Sep 1995g	5756H	355
Thu 25 Sep 2014g	5775H	354
Sat 25 Sep 2060g	5821H	355
Mon 25 Sep 2090g	5851H	353
Mon 26 Sep 1870g	5631H	355
Thu 26 Sep 1889g	5650H	354
Sat 26 Sep 1908g	5669H	355
Mon 26 Sep 1938g	5699H	353
Thu 26 Sep 1946g	5707H	354
Thu 26 Sep 1957g	5718H	354
Mon 26 Sep 2022g	5783H	355
Thu 26 Sep 2041g	5802H	354
Tue 26 Sep 2079g	5840H	354
Thu 26 Sep 2109g	5870H	354
Mon 27 Sep 1897g	5658H	355
Tue 27 Sep 1927g	5688H	354
Mon 27 Sep 1965g	5726H	353
Thu 27 Sep 1973g	5734H	355
Thu 27 Sep 1984g	5745H	354
Sat 27 Sep 2003g	5764H	355
Mon 27 Sep 2049g	5810H	355
Thu 27 Sep 2068g	5829H	354
Sat 27 Sep 2087g	5848H	355
Sat 27 Sep 2098g	5859H	353
Mon 27 Sep 2117g	5878H	355
Sat 28 Sep 1878g	5639H	355
Thu 28 Sep 1916g	5677H	354
Sat 28 Sep 1935g	5696H	355
Tue 28 Sep 1954g	5715H	354
Mon 28 Sep 1992g	5753H	353
Sat 28 Sep 2030g	5791H	355
Mon 28 Sep 2076g	5837H	355
Mon 29 Sep 1924g	5685H	355
Sat 29 Sep 1962g	5723H	355
Tue 29 Sep 1981g	5742H	354
Thu 29 Sep 2011g	5772H	354
Sat 29 Sep 2057g	5818H	355
Thu 29 Sep 2095g	5856H	354
Thu 30 Sep 1875g	5636H	355
Thu 30 Sep 1886g	5647H	354
Sat 30 Sep 1905g	5666H	355
Thu 30 Sep 1943g	5704H	354
Sat 30 Sep 1989g	5750H	355
Sat 30 Sep 2000g	5761H	353
Tue 30 Sep 2008g	5769H	354
Mon 30 Sep 2019g	5780H	355
Thu 30 Sep 2038g	5799H	354
Sat 30 Sep 2084g	5845H	355
Thu 30 Sep 2106g	5867H	354
Mon 1 Oct 1894g	5655H	353
Sat 1 Oct 1932g	5693H	355
Mon 1 Oct 1951g	5712H	355
Thu 1 Oct 1970g	5731H	354
Mon 1 Oct 2046g	5807H	355
Thu 1 Oct 2065g	5826H	354
Mon 1 Oct 2114g	5875H	353
Tue 2 Oct 1883g	5644H	354
Thu 2 Oct 1902g	5663H	355
Thu 2 Oct 1913g	5674H	354
Mon 2 Oct 1978g	5739H	355
Thu 2 Oct 1997g	5758H	354
Sat 2 Oct 2027g	5788H	355
Mon 2 Oct 2073g	5834H	355
Thu 2 Oct 2092g	5853H	354
Tue 2 Oct 2103g	5864H	354
Thu 3 Oct 1872g	5633H	354
Sat 3 Oct 1891g	5652H	355
Mon 3 Oct 1921g	5682H	355
Thu 3 Oct 1940g	5701H	354
Sat 3 Oct 1959g	5720H	355
Mon 3 Oct 2016g	5777H	353
Thu 3 Oct 2024g	5785H	355
Sat 3 Oct 2054g	5815H	355
Sat 3 Oct 2111g	5872H	355
Tue 4 Oct 1910g	5671H	354
Mon 4 Oct 1948g	5709H	355
Sat 4 Oct 1986g	5747H	355
Tue 4 Oct 2005g	5766H	354
Thu 4 Oct 2035g	5796H	354
Sat 4 Oct 2081g	5842H	355
Mon 4 Oct 2100g	5861H	355
Sat 5 Oct 1929g	5690H	353
Thu 5 Oct 1967g	5728H	354
Mon 5 Oct 2043g	5804H	353
Thu 5 Oct 2062g	5823H	354

Note that the years 5754H (1993g), 5830H (2069g), and 5849H (2088g) beginning on September 16 are 12 month years.

To return to the top click here. Separation Dates For other Additional Notes click here. Hebrew Calendar Science and Myths

I'd love to hear from you. Please send your thoughts to:

Remy Landau

First  Paged 29 Dec 1998
Next Revised 26 Jun 2001