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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