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Jewish Calendar Accuracy Test

The Jewish calendar’s calculations attempt to follow the average length of the new moon. But the difference between the Jewish calendar’s average length of a new moon, and the actual length of the new moon is off by a very small amount.

The most accurate difference is -.57 seconds (Dr. Irv Bromberg, COGWA, Jewdaism 101). The approximate value of 3/5 of second is -.6 seconds (Approx. Dr. Irv Bromberg). 2 Millionths of a month is -.17 seconds (Avraham Yaakov Finkel). How much of a difference do any of these make in calculating the dates of the holy days using the Jewish calendar?

Jewish calendar calculations difference (in seconds)

Year range - BCE: (100 years)

to

LOADING

With a -0.57 second correction to the calculation of the Jewish calendar, 77% of the holy days from 1925 to 2025 (100 years) are on the wrong date.

Results summary:
Total on wrong date: 77
Off by 1 day: 12
Off by 2 days: 55
Off by 3 or more days: 10

Earliest month:October, Latest month: November

Error
(days diff.)		 Date
(Jewish Molad)		 Date
(corrected by -0.57 sec.)
2 * 9/19/1925 9/17/1925
3 * 9/9/1926 9/6/1926
1 * 9/27/1927 9/26/1927
2 * 9/15/1928 9/13/1928
2 * 10/5/1929 10/3/1929
1 * 9/23/1930 9/22/1930
0 9/12/1931 9/12/1931
2 * 10/1/1932 9/29/1932
3 * 9/21/1933 9/18/1933
2 * 9/10/1934 9/8/1934
2 * 9/28/1935 9/26/1935
2 * 9/17/1936 9/15/1936
2 * 9/6/1937 9/4/1937
2 * 9/26/1938 9/24/1938
2 * 9/14/1939 9/12/1939
3 * 10/3/1940 9/30/1940
2 * 9/22/1941 9/20/1941
2 * 9/12/1942 9/10/1942
2 * 9/30/1943 9/28/1943
2 * 9/18/1944 9/16/1944
2 * 9/8/1945 9/6/1945
0 9/26/1946 9/26/1946
0 9/15/1947 9/15/1947
2 * 10/4/1948 10/2/1948
2 * 9/24/1949 9/22/1949
1 * 9/12/1950 9/11/1950
2 * 10/1/1951 9/29/1951
2 * 9/20/1952 9/18/1952
3 * 9/10/1953 9/7/1953
1 * 9/28/1954 9/27/1954
2 * 9/17/1955 9/15/1955
2 * 9/6/1956 9/4/1956
3 * 9/26/1957 9/23/1957
2 * 9/15/1958 9/13/1958
2 * 10/3/1959 10/1/1959
3 * 9/22/1960 9/19/1960
2 * 9/11/1961 9/9/1961
0 9/29/1962 9/29/1962
2 * 9/19/1963 9/17/1963
2 * 9/7/1964 9/5/1964
2 * 9/27/1965 9/25/1965
0 9/15/1966 9/15/1966
2 * 10/5/1967 10/3/1967
2 * 9/23/1968 9/21/1968
2 * 9/13/1969 9/11/1969
0 10/1/1970 10/1/1970
0 9/20/1971 9/20/1971
2 * 9/9/1972 9/7/1972
0 9/27/1973 9/27/1973
1 * 9/17/1974 9/16/1974
0 9/6/1975 9/6/1975
2 * 9/25/1976 9/23/1976
1 * 9/13/1977 9/12/1977
0 10/2/1978 10/2/1978
2 * 9/22/1979 9/20/1979
3 * 9/11/1980 9/8/1980
1 * 9/29/1981 9/28/1981
0 9/18/1982 9/18/1982
2 * 9/8/1983 9/6/1983
3 * 9/27/1984 9/24/1984
2 * 9/16/1985 9/14/1985
2 * 10/4/1986 10/2/1986
2 * 9/24/1987 9/22/1987
2 * 9/12/1988 9/10/1988
0 9/30/1989 9/30/1989
0 9/20/1990 9/20/1990
0 9/9/1991 9/9/1991
2 * 9/28/1992 9/26/1992
0 9/16/1993 9/16/1993
1 * 9/6/1994 9/5/1994
2 * 9/25/1995 9/23/1995
2 * 9/14/1996 9/12/1996
0 10/2/1997 10/2/1997
0 9/21/1998 9/21/1998
2 * 9/11/1999 9/9/1999
2 * 9/30/2000 9/28/2000
1 * 9/18/2001 9/17/2001
0 9/7/2002 9/7/2002
2 * 9/27/2003 9/25/2003
3 * 9/16/2004 9/13/2004
1 * 10/4/2005 10/3/2005
2 * 9/23/2006 9/21/2006
2 * 9/13/2007 9/11/2007
1 * 9/30/2008 9/29/2008
0 9/19/2009 9/19/2009
2 * 9/9/2010 9/7/2010
3 * 9/29/2011 9/26/2011
2 * 9/17/2012 9/15/2012
0 9/5/2013 9/5/2013
2 * 9/25/2014 9/23/2014
2 * 9/14/2015 9/12/2015
2 * 10/3/2016 10/1/2016
0 9/21/2017 9/21/2017
0 9/10/2018 9/10/2018
2 * 9/30/2019 9/28/2019
2 * 9/19/2020 9/17/2020
1 * 9/7/2021 9/6/2021
2 * 9/26/2022 9/24/2022
2 * 9/16/2023 9/14/2023
0 10/3/2024 10/3/2024

* This year has a difference between the inaccurate measurements of the average cycle of the new moon conjunction of the Jewish calendar compared to the corrected measurements.