Type of year C on a solar calendar according to its starting and ending days in the week
A common year starting on Friday is any non-leap year (i.e. a year with 365 days) that begins on Friday , 1 January, and ends on Friday, 31 December. Its dominical letter hence is C . 2021 , the current year, is a common year starting on a Friday in the Gregorian calendar . The last such year was 2010 and the next such year will be 2027 in the Gregorian calendar,[1] or, likewise, 2005 , 2011 and 2022 in the obsolete Julian calendar . The century year, 2100 , will also be a common year starting on Friday in the Gregorian calendar . See below for more . Any common year that starts on Wednesday , Friday or Saturday has only one Friday the 13th ; the only Friday the 13th in this common year occurs in August . Leap year starting on Thursday share this characteristic, but also have another one in February . In this common year, February is rectangular in ISO 8601 calendar, U.S. Independence Day and Halloween are on a Sunday , Memorial Day is on its latest possible date, May 31 , Labor Day is on September 6 , Thanksgiving Day is on November 25 , and Christmas is on a Saturday . This is one of the three possible common years in which an end of century year can begin on, the most recent being 1700 and the next one being 2100.
Calendar for any common year starting on Friday, presented as common in many English-speaking areas
January
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
February
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
March
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
April
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
May
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
June
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
July
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
August
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
September
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
October
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
November
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
December
Su
Mo
Tu
We
Th
Fr
Sa
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
ISO 8601 -conformant calendar with week numbers for any common year starting on Friday (dominical letter C)
January
Wk
Mo
Tu
We
Th
Fr
Sa
Su
53
01
02
03
01
04
05
06
07
08
09
10
02
11
12
13
14
15
16
17
03
18
19
20
21
22
23
24
04
25
26
27
28
29
30
31
February
Wk
Mo
Tu
We
Th
Fr
Sa
Su
05
01
02
03
04
05
06
07
06
08
09
10
11
12
13
14
07
15
16
17
18
19
20
21
08
22
23
24
25
26
27
28
March
Wk
Mo
Tu
We
Th
Fr
Sa
Su
09
01
02
03
04
05
06
07
10
08
09
10
11
12
13
14
11
15
16
17
18
19
20
21
12
22
23
24
25
26
27
28
13
29
30
31
April
Wk
Mo
Tu
We
Th
Fr
Sa
Su
13
01
02
03
04
14
05
06
07
08
09
10
11
15
12
13
14
15
16
17
18
16
19
20
21
22
23
24
25
17
26
27
28
29
30
May
Wk
Mo
Tu
We
Th
Fr
Sa
Su
17
01
02
18
03
04
05
06
07
08
09
19
10
11
12
13
14
15
16
20
17
18
19
20
21
22
23
21
24
25
26
27
28
29
30
22
31
June
Wk
Mo
Tu
We
Th
Fr
Sa
Su
22
01
02
03
04
05
06
23
07
08
09
10
11
12
13
24
14
15
16
17
18
19
20
25
21
22
23
24
25
26
27
26
28
29
30
July
Wk
Mo
Tu
We
Th
Fr
Sa
Su
26
01
02
03
04
27
05
06
07
08
09
10
11
28
12
13
14
15
16
17
18
29
19
20
21
22
23
24
25
30
26
27
28
29
30
31
August
Wk
Mo
Tu
We
Th
Fr
Sa
Su
30
01
31
02
03
04
05
06
07
08
32
09
10
11
12
13
14
15
33
16
17
18
19
20
21
22
34
23
24
25
26
27
28
29
35
30
31
September
Wk
Mo
Tu
We
Th
Fr
Sa
Su
35
01
02
03
04
05
36
06
07
08
09
10
11
12
37
13
14
15
16
17
18
19
38
20
21
22
23
24
25
26
39
27
28
29
30
October
Wk
Mo
Tu
We
Th
Fr
Sa
Su
39
01
02
03
40
04
05
06
07
08
09
10
41
11
12
13
14
15
16
17
42
18
19
20
21
22
23
24
43
25
26
27
28
29
30
31
November
Wk
Mo
Tu
We
Th
Fr
Sa
Su
44
01
02
03
04
05
06
07
45
08
09
10
11
12
13
14
46
15
16
17
18
19
20
21
47
22
23
24
25
26
27
28
48
29
30
December
Wk
Mo
Tu
We
Th
Fr
Sa
Su
48
01
02
03
04
05
49
06
07
08
09
10
11
12
50
13
14
15
16
17
18
19
51
20
21
22
23
24
25
26
52
27
28
29
30
31
This is the only year type where the n th "Doomsday " (this year Sunday) is not in ISO week n ; it is in ISO week n -1.
Applicable years [ edit ]
Gregorian Calendar [ edit ]
In the (currently used) Gregorian calendar, alongside Sunday , Monday , Wednesday or Saturday , the fourteen types of year (seven common, seven leap) repeat in a 400-year cycle (20871 weeks). Forty-three common years per cycle or exactly 10.75% start on a Friday. The 28-year sub-cycle does only span across century years divisible by 400, e.g. 1600, 2000, and 2400.
Julian Calendar [ edit ]
In the now-obsolete Julian calendar, the fourteen types of year (seven common, seven leap) repeat in a 28-year cycle (1461 weeks). A leap year has two adjoining dominical letters (one for January and February and the other for March to December, as 29 February has no letter). This sequence occurs exactly once within a cycle, and every common letter thrice.
As the Julian calendar repeats after 28 years that means it will also repeat after 700 years, i.e. 25 cycles. The year's position in the cycle is given by the formula ((year + 8) mod 28) + 1). Years 4, 15 and 26 of the cycle are common years beginning on Friday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Friday.
Julian common years starting on Friday
Decade
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
10th
15th century
1406
1417
1423
1434
1445
1451
1462
1473
1479
1490
—
16th century
1501
1507
1518
1529
1535
1546
1557
1563
1574
1585
1591
—
17th century
1602
1613
1619
1630
—
1641
1647
1658
1669
1675
1686
1697
18th century
1703
1714
1725
1731
1742
1753
1759
1770
—
1781
1787
1798
19th century
1809
1815
1826
1837
1843
1854
1865
1871
1882
1893
1899
20th century
1910
—
1921
1927
1938
1949
1955
1966
1977
1983
1994
21st century
2005
2011
2022
2033
2039
2050
—
2061
2067
2078
2089
2095
Gregorian year types per leap cycle by Dominical letter (DL)[2] and Doomsday (DD)
Year starts
Common years
Leap years
1 Jan
Count
Ratio
31 Dec
DL
DD
Count
Ratio
31 Dec
DL
DD
Count
Ratio
Sun
58
14.50 %
Sun
A
Tue
43
10.75 %
Mon
AG
Wed
15
0 3.75 %
Sat
56
14.00 %
Sat
B
Mon
43
10.75 %
Sun
BA
Tue
13
0 3.25 %
Fri
58
14.50 %
Fri
C
Sun
43
10.75 %
Sat
CB
Mon
15
0 3.75 %
Thu
57
14.25 %
Thu
D
Sat
44
11.00 %
Fri
DC
Sun
13
0 3.25 %
Wed
57
14.25 %
Wed
E
Fri
43
10.75 %
Thu
ED
Sat
14
0 3.50 %
Tue
58
14.50 %
Tue
F
Thu
44
11.00 %
Wed
FE
Fri
14
0 3.50 %
Mon
56
14.00 %
Mon
G
Wed
43
10.75 %
Tue
GF
Thu
13
0 3.25 %
∑
400
100.0 %
303
75.75 %
97
24.25 %
References [ edit ]