From Wikipedia, the free encyclopedia
The solar cycle is a 28-year cycle of the Julian calendar , and 400-year cycle of the Gregorian calendar with respect to the week . It occurs because leap years occur every 4 years and there are 7 possible days to start a leap year , making a 28-year sequence.
This cycle also occurs in the Gregorian calendar , but it is interrupted by years such as 1700, 1800, 1900, 2100, 2200, 2300 and 2500, which are divisible by four but which are common years . This interruption has the effect of skipping 16 years of the solar cycle between February 28 and March 1. Because the Gregorian cycle of 400 years has exactly 146,097 days, i.e. exactly 20,871 weeks, one can say that the Gregorian so-called solar cycle lasts 400 years.
Calendar years are usually marked by Dominical letters indicating the first Sunday in a new year, thus the term solar cycle can also refer to a repeating sequence of Dominical letters.
Unless a year is not a leap year due to Gregorian exceptions, a sequence of calendars is reused every 28 years.
The name solar cycle comes from Sunday , the traditional first day of the week .
Examples
Julian calendar
The dominical letter in the Julian calendar depends only on the remainder of the year mod 28.
Year mod 28
Dominical letter
0
DC
1
B
2
A
3
G
4
FE
5
D
6
C
7
B
8
AG
9
F
10
E
11
D
12
CB
13
A
14
G
15
F
16
ED
17
C
18
B
19
A
20
GF
21
E
22
D
23
C
24
BA
25
G
26
F
27
E
Year mod 28
Doomsday
0
Sunday
1
Monday
2
Tuesday
3
Wednesday
4
Friday
5
Saturday
6
Sunday
7
Monday
8
Wednesday
9
Thursday
10
Friday
11
Saturday
12
Monday
13
Tuesday
14
Wednesday
15
Thursday
16
Saturday
17
Sunday
18
Monday
19
Tuesday
20
Thursday
21
Friday
22
Saturday
23
Sunday
24
Tuesday
25
Wednesday
26
Thursday
27
Friday
Friday the 13ths
Year mod 28
1st
2nd
3rd
0
February 13
August 13
1
May 13
2
January 13
October 13
3
April 13
July 13
4
June 13
5
February 13
March 13
November 13
6
August 13
7
May 13
8
January 13
April 13
July 13
9
September 13
December 13
10
June 13
11
February 13
March 13
November 13
12
May 13
13
January 13
October 13
14
April 13
July 13
15
September 13
December 13
16
March 13
November 13
17
August 13
18
May 13
19
January 13
October 13
20
September 13
December 13
21
June 13
22
February 13
March 13
November 13
23
August 13
24
October 13
25
April 13
July 13
26
September 13
December 13
27
June 13
Gregorian calendar
The years 1700, 1800, and 1900 were not leap years (unlike the Julian calendar) and do not fit in the tables of Dominical letters below.
Century
Year
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
1600
2000
Tue
Wed
Thu
Fri
Sat
Sun
Mon
1700
2100
Sun
Mon
Tue
Wed
Thu
Fri
Sat
1800
2200
Fri
Sat
Sun
Mon
Tue
Wed
Thu
1900
2300
Wed
Thu
Fri
Sat
Sun
Mon
Tue
First days of months
Year
Month
January
February
March
April
May
June
July
August
September
October
November
December
2000
2028
2056
2084
Saturday
Tuesday
Wednesday
Saturday
Monday
Thursday
Saturday
Tuesday
Friday
Sunday
Wednesday
Friday
2001
2029
2057
2085
Monday
Thursday
Thursday
Sunday
Tuesday
Friday
Sunday
Wednesday
Saturday
Monday
Thursday
Saturday
2002
2030
2058
2086
Tuesday
Friday
Friday
Monday
Wednesday
Saturday
Monday
Thursday
Sunday
Tuesday
Friday
Sunday
2003
2031
2059
2087
Wednesday
Saturday
Saturday
Tuesday
Thursday
Sunday
Tuesday
Friday
Monday
Wednesday
Saturday
Monday
2004
2032
2060
2088
Thursday
Sunday
Monday
Thursday
Saturday
Tuesday
Thursday
Sunday
Wednesday
Friday
Monday
Wednesday
2005
2033
2061
2089
Saturday
Tuesday
Tuesday
Friday
Sunday
Wednesday
Friday
Monday
Thursday
Saturday
Tuesday
Thursday
2006
2034
2062
2090
Sunday
Wednesday
Wednesday
Saturday
Monday
Thursday
Saturday
Tuesday
Friday
Sunday
Wednesday
Friday
2007
2035
2063
2091
Monday
Thursday
Thursday
Sunday
Tuesday
Friday
Sunday
Wednesday
Saturday
Monday
Thursday
Saturday
2008
2036
2064
2092
Tuesday
Friday
Saturday
Tuesday
Thursday
Sunday
Tuesday
Friday
Monday
Wednesday
Saturday
Monday
2009
2037
2065
2093
Thursday
Sunday
Sunday
Wednesday
Friday
Monday
Wednesday
Saturday
Tuesday
Thursday
Sunday
Tuesday
2010
2038
2066
2094
Friday
Monday
Monday
Thursday
Saturday
Tuesday
Thursday
Sunday
Wednesday
Friday
Monday
Wednesday
2011
2039
2067
2095
Saturday
Tuesday
Tuesday
Friday
Sunday
Wednesday
Friday
Monday
Thursday
Saturday
Tuesday
Thursday
2012
2040
2068
2096
Sunday
Wednesday
Thursday
Sunday
Tuesday
Friday
Sunday
Wednesday
Saturday
Monday
Thursday
Saturday
2013
2041
2069
2097
Tuesday
Friday
Friday
Monday
Wednesday
Saturday
Monday
Thursday
Sunday
Tuesday
Friday
Sunday
2014
2042
2070
2098
Wednesday
Saturday
Saturday
Tuesday
Thursday
Sunday
Tuesday
Friday
Monday
Wednesday
Saturday
Monday
2015
2043
2071
2099
Thursday
Sunday
Sunday
Wednesday
Friday
Monday
Wednesday
Saturday
Tuesday
Thursday
Sunday
Tuesday
2016
2044
2072
Friday
Monday
Tuesday
Friday
Sunday
Wednesday
Friday
Monday
Thursday
Saturday
Tuesday
Thursday
2017
2045
2073
Sunday
Wednesday
Wednesday
Saturday
Monday
Thursday
Saturday
Tuesday
Friday
Sunday
Wednesday
Friday
2018
2046
2074
Monday
Thursday
Thursday
Sunday
Tuesday
Friday
Sunday
Wednesday
Saturday
Monday
Thursday
Saturday
2019
2047
2075
Tuesday
Friday
Friday
Monday
Wednesday
Saturday
Monday
Thursday
Sunday
Tuesday
Friday
Sunday
2020
2048
2076
Wednesday
Saturday
Sunday
Wednesday
Friday
Monday
Wednesday
Saturday
Tuesday
Thursday
Sunday
Tuesday
2021
2049
2077
Friday
Monday
Monday
Thursday
Saturday
Tuesday
Thursday
Sunday
Wednesday
Friday
Monday
Wednesday
2022
2050
2078
Saturday
Tuesday
Tuesday
Friday
Sunday
Wednesday
Friday
Monday
Thursday
Saturday
Tuesday
Thursday
2023
2051
2079
Sunday
Wednesday
Wednesday
Saturday
Monday
Thursday
Saturday
Tuesday
Friday
Sunday
Wednesday
Friday
2024
2052
2080
Monday
Thursday
Friday
Monday
Wednesday
Saturday
Monday
Thursday
Sunday
Tuesday
Friday
Sunday
2025
2053
2081
Wednesday
Saturday
Saturday
Tuesday
Thursday
Sunday
Tuesday
Friday
Monday
Wednesday
Saturday
Monday
2026
2054
2082
Thursday
Sunday
Sunday
Wednesday
Friday
Monday
Wednesday
Saturday
Tuesday
Thursday
Sunday
Tuesday
2027
2055
2083
Friday
Monday
Monday
Thursday
Saturday
Tuesday
Thursday
Sunday
Wednesday
Friday
Monday
Wednesday
1583–1699
1583–1600
1601–1628
1629–1656
1657–1684
1685–1699
Dominical letter
1601
1629
1657
1685
G
1602
1630
1658
1686
F
1603
1631
1659
1687
E
1604
1632
1660
1688
DC
1605
1633
1661
1689
B
1606
1634
1662
1690
A
1607
1635
1663
1691
G
1608
1636
1664
1692
FE
1609
1637
1665
1693
D
1610
1638
1666
1694
C
1583
1611
1639
1667
1695
B
1584
1612
1640
1668
1696
AG
1585
1613
1641
1669
1697
F
1586
1614
1642
1670
1698
E
1587
1615
1643
1671
1699
D
1588
1616
1644
1672
CB
1589
1617
1645
1673
A
1590
1618
1646
1674
G
1591
1619
1647
1675
F
1592
1620
1648
1676
ED
1593
1621
1649
1677
C
1594
1622
1650
1678
B
1595
1623
1651
1679
A
1596
1624
1652
1680
GF
1597
1625
1653
1681
E
1598
1626
1654
1682
D
1599
1627
1655
1683
C
1600
1628
1656
1684
BA
1701–1799
1701–1728
1729–1756
1757–1784
1785–1799
Dominical letter
1701
1729
1757
1785
B
1702
1730
1758
1786
A
1703
1731
1759
1787
G
1704
1732
1760
1788
FE
1705
1733
1761
1789
D
1706
1734
1762
1790
C
1707
1735
1763
1791
B
1708
1736
1764
1792
AG
1709
1737
1765
1793
F
1710
1738
1766
1794
E
1711
1739
1767
1795
D
1712
1740
1768
1796
CB
1713
1741
1769
1797
A
1714
1742
1770
1798
G
1715
1743
1771
1799
F
1716
1744
1772
ED
1717
1745
1773
C
1718
1746
1774
B
1719
1747
1775
A
1720
1748
1776
GF
1721
1749
1777
E
1722
1750
1778
D
1723
1751
1779
C
1724
1752
1780
BA
1725
1753
1781
G
1726
1754
1782
F
1727
1755
1783
E
1728
1756
1784
DC
1801–1899
1801–1828
1829–1856
1857–1884
1885–1899
Dominical letter
1801
1829
1857
1885
D
1802
1830
1858
1886
C
1803
1831
1859
1887
B
1804
1832
1860
1888
AG
1805
1833
1861
1889
F
1806
1834
1862
1890
E
1807
1835
1863
1891
D
1808
1836
1864
1892
CB
1809
1837
1865
1893
A
1810
1838
1866
1894
G
1811
1839
1867
1895
F
1812
1840
1868
1896
ED
1813
1841
1869
1897
C
1814
1842
1870
1898
B
1815
1843
1871
1899
A
1816
1844
1872
GF
1817
1845
1873
E
1818
1846
1874
D
1819
1847
1875
C
1820
1848
1876
BA
1821
1849
1877
G
1822
1850
1878
F
1823
1851
1879
E
1824
1852
1880
DC
1825
1853
1881
B
1826
1854
1882
A
1827
1855
1883
G
1828
1856
1884
FE
1901–2099
1901–1928
1929–1956
1957–1984
1985–2012
2013–2040
2041–2068
2069–2096
2097–2099
Dominical letter
1901
1929
1957
1985
2013
2041
2069
2097
F
1902
1930
1958
1986
2014
2042
2070
2098
E
1903
1931
1959
1987
2015
2043
2071
2099
D
1904
1932
1960
1988
2016
2044
2072
CB
1905
1933
1961
1989
2017
2045
2073
A
1906
1934
1962
1990
2018
2046
2074
G
1907
1935
1963
1991
2019
2047
2075
F
1908
1936
1964
1992
2020
2048
2076
ED
1909
1937
1965
1993
2021
2049
2077
C
1910
1938
1966
1994
2022
2050
2078
B
1911
1939
1967
1995
2023
2051
2079
A
1912
1940
1968
1996
2024
2052
2080
GF
1913
1941
1969
1997
2025
2053
2081
E
1914
1942
1970
1998
2026
2054
2082
D
1915
1943
1971
1999
2027
2055
2083
C
1916
1944
1972
2000
2028
2056
2084
BA
1917
1945
1973
2001
2029
2057
2085
G
1918
1946
1974
2002
2030
2058
2086
F
1919
1947
1975
2003
2031
2059
2087
E
1920
1948
1976
2004
2032
2060
2088
DC
1921
1949
1977
2005
2033
2061
2089
B
1922
1950
1978
2006
2034
2062
2090
A
1923
1951
1979
2007
2035
2063
2091
G
1924
1952
1980
2008
2036
2064
2092
FE
1925
1953
1981
2009
2037
2065
2093
D
1926
1954
1982
2010
2038
2066
2094
C
1927
1955
1983
2011
2039
2067
2095
B
1928
1956
1984
2012
2040
2068
2096
AG
See also
External links