Type of year AG on a solar calendar according to its starting and ending days in the week
A leap year starting on Sunday is any year with 366 days (i.e. it includes 29 February) that begins on Sunday, 1 January, and ends on Monday, 31 December. Its dominical letters hence are AG. The most recent year of such kind was 2012 and the next one will be 2040 in the Gregorian calendar[1] or, likewise 2024 and 2052 in the obsolete Julian calendar.
This is the only leap year with three occurrences of Friday the 13th: those three in this leap year occur three months (13 weeks) apart: in January, April, and July. Common years starting on Thursday share this characteristic, in the months of February, March, and November.
In this type of year, all dates (except 29 February) fall on their respective weekdays the maximal 58 times in the 400 year Gregorian calendar cycle. Leap years starting on Friday share this characteristic. Additionally, these types of years are the only ones which contain 54 different calendar weeks (2 partial, 52 in full) in areas of the world where Monday is considered the first day of the week.
Calendars
Calendar for any leap year starting on Sunday, 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
29
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 leap year starting on Sunday (dominical letter AG)
January
Wk
Mo
Tu
We
Th
Fr
Sa
Su
52
01
01
02
03
04
05
06
07
08
02
09
10
11
12
13
14
15
03
16
17
18
19
20
21
22
04
23
24
25
26
27
28
29
05
30
31
February
Wk
Mo
Tu
We
Th
Fr
Sa
Su
05
01
02
03
04
05
06
06
07
08
09
10
11
12
07
13
14
15
16
17
18
19
08
20
21
22
23
24
25
26
09
27
28
29
March
Wk
Mo
Tu
We
Th
Fr
Sa
Su
09
01
02
03
04
10
05
06
07
08
09
10
11
11
12
13
14
15
16
17
18
12
19
20
21
22
23
24
25
13
26
27
28
29
30
31
April
Wk
Mo
Tu
We
Th
Fr
Sa
Su
13
01
14
02
03
04
05
06
07
08
15
09
10
11
12
13
14
15
16
16
17
18
19
20
21
22
17
23
24
25
26
27
28
29
18
30
May
Wk
Mo
Tu
We
Th
Fr
Sa
Su
18
01
02
03
04
05
06
19
07
08
09
10
11
12
13
20
14
15
16
17
18
19
20
21
21
22
23
24
25
26
27
22
28
29
30
31
June
Wk
Mo
Tu
We
Th
Fr
Sa
Su
22
01
02
03
23
04
05
06
07
08
09
10
24
11
12
13
14
15
16
17
25
18
19
20
21
22
23
24
26
25
26
27
28
29
30
July
Wk
Mo
Tu
We
Th
Fr
Sa
Su
26
01
27
02
03
04
05
06
07
08
28
09
10
11
12
13
14
15
29
16
17
18
19
20
21
22
30
23
24
25
26
27
28
29
31
30
31
August
Wk
Mo
Tu
We
Th
Fr
Sa
Su
31
01
02
03
04
05
32
06
07
08
09
10
11
12
33
13
14
15
16
17
18
19
34
20
21
22
23
24
25
26
35
27
28
29
30
31
September
Wk
Mo
Tu
We
Th
Fr
Sa
Su
35
01
02
36
03
04
05
06
07
08
09
37
10
11
12
13
14
15
16
38
17
18
19
20
21
22
23
39
24
25
26
27
28
29
30
October
Wk
Mo
Tu
We
Th
Fr
Sa
Su
40
01
02
03
04
05
06
07
41
08
09
10
11
12
13
14
42
15
16
17
18
19
20
21
43
22
23
24
25
26
27
28
44
29
30
31
November
Wk
Mo
Tu
We
Th
Fr
Sa
Su
44
01
02
03
04
45
05
06
07
08
09
10
11
46
12
13
14
15
16
17
18
47
19
20
21
22
23
24
25
48
26
27
28
29
30
December
Wk
Mo
Tu
We
Th
Fr
Sa
Su
48
01
02
49
03
04
05
06
07
08
09
50
10
11
12
13
14
15
16
51
17
18
19
20
21
22
23
52
24
25
26
27
28
29
30
01
31
Applicable years
Gregorian Calendar
Leap years that begin on Sunday, along with those starting on Friday, occur most frequently: 15 of the 97 (≈ 15.46%) total leap years in a 400-year cycle of the Gregorian calendar. Thus, their overall occurrence is 3.75% (15 out of 400).
Like all leap year types, the one starting with 1 January on a Sunday occurs exactly once in a 28-year cycle in the Julian calendar, i.e., in 3.57% of years. As the Julian calendar repeats after 28 years, it will also repeat after 700 years, i.e., 25 cycles. The formula gives the year's position in the cycle ((year + 8) mod 28) + 1).
Daylight saving begins on its latest possible date, September 30 in New Zealand and October 7 in Australia – this is the only leap year where the period of standard time over the winter months lasts 26 weeks in New Zealand and 27 weeks in Australia (in all other leap years, it lasts only 25 weeks in New Zealand and 26 weeks in Australia)