Solar cycle (calendar)

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.[1]

This cycle also occurs in the Gregorian calendar, but it is interrupted by years such as 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.[2]

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.[3]

The name solar cycle comes from Sunday, the traditional first day of the week.

ExamplesEdit

Julian calendarEdit

Dominical letterEdit

The dominical letter in the Julian calendar depends only on the remainder of the year mod 28.[4]

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

DoomsdayEdit

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 13thsEdit

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 calendarEdit

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.

DoomsdayEdit

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

See alsoEdit

ReferencesEdit

  1. ^ Alexander Philip (2012). The Calendar: Its History, Structure and Improvement. Cambridge University Press. p. 45. ISBN 9781107640214.
  2. ^ Stephen G. Christianson (2000). The American Book of Days. H.W. Wilson. p. 875. ISBN 9780824209544.
  3. ^ Jacques Ozanam (1840). Recreations in mathematics and natural philosophy, recomposed by m. Montucla and tr. by C. Hutton. p. 486.
  4. ^ George Crabb (1823). Universal Technological Dictionary: Or, Familiar Explanations of the Terms Used in All Arts and Sciences. Baldwin, Cradock, and Joy. p. 93.

Further readingEdit

  • C. R. Cheney (rev. Michael Jones), 2012: Handbook of dates (2nd edition), CUP

External linksEdit