This is the only common year with three occurrences of Friday the 13th: those three in this common year occur in February, March, and November. Leap years starting on Sunday share this characteristic and with the exception of skipped leap years, a leap year that begins on a Sunday falls exactly three years either side of two consecutive common years starting on Thursday - for example 2012 between 2009 and 2015. From February until March in this type of year is also the shortest period (one month) that runs between two instances of Friday the 13th.
In this common year, February is rectangular in calendar where weeks start on a Sunday, Martin Luther King Jr. Day is on January 19, Valentine’s Day is on a Saturday, President's Day is on February 16, Saint Patrick’s Day is on a Tuesday, Memorial Day is on its earliest possible date, May 25, U.S. Independence Day and Halloween are on a Saturday, Labor Day is on its latest possible date, September 7, Veterans Day is on a Wednesday, Thanksgiving is on November 26, and Christmas is on a Friday. This common year is also the only one where Memorial Day and Labor Day are not 14 weeks (98 days) apart: they are 15 weeks (105 days) apart in this common year. Leap years starting on Wednesday share this characteristic. Like leap years starting on Wednesday, this common year also has the shortest gap between Halloween (October 31) and the end of Daylight Saving Time in the US (November 1) by one day as of 2007. Prior to 2007, this common year had the longest gap between the end of Daylight Saving Time in the US (October 25) and Halloween by 6 days. Also, Daylight Savings Time begins and ends on their earliest possible dates, March 8 and November 1 respectively, in this common year as of 2007. Daylight Savings Time also ended on its earliest possible date prior to 2007, since the difference between the old and new Daylight Savings Times end dates is 7 days. The last common year when Daylight Savings Time ended on October 25 was 1998, and the first common year when it ended on November 1 is 2009.
Calendar for any common year starting on Thursday, presented as common in many English-speaking areas
January
Su
Mo
Tu
We
Th
Fr
Sa
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
February
Su
Mo
Tu
We
Th
Fr
Sa
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
March
Su
Mo
Tu
We
Th
Fr
Sa
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
April
Su
Mo
Tu
We
Th
Fr
Sa
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
May
Su
Mo
Tu
We
Th
Fr
Sa
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
June
Su
Mo
Tu
We
Th
Fr
Sa
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
July
Su
Mo
Tu
We
Th
Fr
Sa
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
August
Su
Mo
Tu
We
Th
Fr
Sa
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
September
Su
Mo
Tu
We
Th
Fr
Sa
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
October
Su
Mo
Tu
We
Th
Fr
Sa
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
November
Su
Mo
Tu
We
Th
Fr
Sa
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
December
Su
Mo
Tu
We
Th
Fr
Sa
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
ISO 8601-conformant calendar with week numbers for any common year starting on Thursday (dominical letter D)
January
Wk
Mo
Tu
We
Th
Fr
Sa
Su
01
01
02
03
04
02
05
06
07
08
09
10
11
03
12
13
14
15
16
17
18
04
19
20
21
22
23
24
25
05
26
27
28
29
30
31
February
Wk
Mo
Tu
We
Th
Fr
Sa
Su
05
01
06
02
03
04
05
06
07
08
07
09
10
11
12
13
14
15
08
16
17
18
19
20
21
22
09
23
24
25
26
27
28
March
Wk
Mo
Tu
We
Th
Fr
Sa
Su
09
01
10
02
03
04
05
06
07
08
11
09
10
11
12
13
14
15
12
16
17
18
19
20
21
22
13
23
24
25
26
27
28
29
14
30
31
April
Wk
Mo
Tu
We
Th
Fr
Sa
Su
14
01
02
03
04
05
15
06
07
08
09
10
11
12
16
13
14
15
16
17
18
19
17
20
21
22
23
24
25
26
18
27
28
29
30
May
Wk
Mo
Tu
We
Th
Fr
Sa
Su
18
01
02
03
19
04
05
06
07
08
09
10
20
11
12
13
14
15
16
17
21
18
19
20
21
22
23
24
22
25
26
27
28
29
30
31
June
Wk
Mo
Tu
We
Th
Fr
Sa
Su
23
01
02
03
04
05
06
07
24
08
09
10
11
12
13
14
25
15
16
17
18
19
20
21
26
22
23
24
25
26
27
28
27
29
30
July
Wk
Mo
Tu
We
Th
Fr
Sa
Su
27
01
02
03
04
05
28
06
07
08
09
10
11
12
29
13
14
15
16
17
18
19
30
20
21
22
23
24
25
26
31
27
28
29
30
31
August
Wk
Mo
Tu
We
Th
Fr
Sa
Su
31
01
02
32
03
04
05
06
07
08
09
33
10
11
12
13
14
15
16
34
17
18
19
20
21
22
23
35
24
25
26
27
28
29
30
36
31
September
Wk
Mo
Tu
We
Th
Fr
Sa
Su
36
01
02
03
04
05
06
37
07
08
09
10
11
12
13
38
14
15
16
17
18
19
20
39
21
22
23
24
25
26
27
40
28
29
30
October
Wk
Mo
Tu
We
Th
Fr
Sa
Su
40
01
02
03
04
41
05
06
07
08
09
10
11
42
12
13
14
15
16
17
18
43
19
20
21
22
23
24
25
44
26
27
28
29
30
31
November
Wk
Mo
Tu
We
Th
Fr
Sa
Su
44
01
45
02
03
04
05
06
07
08
46
09
10
11
12
13
14
15
47
16
17
18
19
20
21
22
48
23
24
25
26
27
28
29
49
30
December
Wk
Mo
Tu
We
Th
Fr
Sa
Su
49
01
02
03
04
05
06
50
07
08
09
10
11
12
13
51
14
15
16
17
18
19
20
52
21
22
23
24
25
26
27
53
28
29
30
31
Applicable years[]
Gregorian Calendar[]
In the (currently used) Gregorian calendar, alongside Tuesday, the fourteen types of year (seven common, seven leap) repeat in a 400-year cycle (20871 weeks). Forty-four common years per cycle or exactly 11% start on a Thursday. The 28-year sub-cycle only spans across century years divisible by 400, e.g. 1600, 2000, and 2400.
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 3, 14 and 20 of the cycle are common years beginning on Thursday. 2017 is year 10 of the cycle. Approximately 10.71% of all years are common years beginning on Thursday.