Dominical letter

The dominical letter is a letter or two associated with each year that tells one which days of the year are Sundays. January 1 to 7 are always considered A to G, after which the cycle repeats to the end of the year (ignoring February 29 in leap years). Common years have one dominical letter, while leap years have two. For example, the dominical letter of the current year (2023) is A.

Days of the year

Dominical letters for the days of the year
Month	1	2	3	4	5	6	7
	8	9	10	11	12	13	14
	15	16	17	18	19	20	21
	22	23	24	25	26	27	28
	(29)	(30)	(31)
January	A	B	C	D	E	F	G
February	D	E	F	G	A	B	C
March	D	E	F	G	A	B	C
April	G	A	B	C	D	E	F
May	B	C	D	E	F	G	A
June	E	F	G	A	B	C	D
July	G	A	B	C	D	E	F
August	C	D	E	F	G	A	B
September	F	G	A	B	C	D	E
October	A	B	C	D	E	F	G
November	D	E	F	G	A	B	C
December	F	G	A	B	C	D	E

Julian calendar

The Julian calendar repeats every 28 years.

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

Gregorian calendar

The Gregorian calendar repeats every 400 years.

Dominical letter
Year mod 400	+0	+1	+2	+3	+4	+5	+6	+7	+8	+9
0–99
0	BA	G	F	E	DC	B	A	G	FE	D
10	C	B	AG	F	E	D	CB	A	G	F
20	ED	C	B	A	GF	E	D	C	BA	G
30	F	E	DC	B	A	G	FE	D	C	B
40	AG	F	E	D	CB	A	G	F	ED	C
50	B	A	GF	E	D	C	BA	G	F	E
60	DC	B	A	G	FE	D	C	B	AG	F
70	E	D	CB	A	G	F	ED	C	B	A
80	GF	E	D	C	BA	G	F	E	DC	B
90	A	G	FE	D	C	B	AG	F	E	D
100–199
100	C	B	A	G	FE	D	C	B	AG	F
110	E	D	CB	A	G	F	ED	C	B	A
120	GF	E	D	C	BA	G	F	E	DC	B
130	A	G	FE	D	C	B	AG	F	E	D
140	CB	A	G	F	ED	C	B	A	GF	E
150	D	C	BA	G	F	E	DC	B	A	G
160	FE	D	C	B	AG	F	E	D	CB	A
170	G	F	ED	C	B	A	GF	E	D	C
180	BA	G	F	E	DC	B	A	G	FE	D
190	C	B	AG	F	E	D	CB	A	G	F
200–299
200	E	D	C	B	AG	F	E	D	CB	A
210	G	F	ED	C	B	A	GF	E	D	C
220	BA	G	F	E	DC	B	A	G	FE	D
230	C	B	AG	F	E	D	CB	A	G	F
240	ED	C	B	A	GF	E	D	C	BA	G
250	F	E	DC	B	A	G	FE	D	C	B
260	AG	F	E	D	CB	A	G	F	ED	C
270	B	A	GF	E	D	C	BA	G	F	E
280	DC	B	A	G	FE	D	C	B	AG	F
290	E	D	CB	A	G	F	ED	C	B	A
300–399
300	G	F	E	D	CB	A	G	F	ED	C
310	B	A	GF	E	D	C	BA	G	F	E
320	DC	B	A	G	FE	D	C	B	AG	F
330	E	D	CB	A	G	F	ED	C	B	A
340	GF	E	D	C	BA	G	F	E	DC	B
350	A	G	FE	D	C	B	AG	F	E	D
360	CB	A	G	F	ED	C	B	A	GF	E
370	D	C	BA	G	F	E	DC	B	A	G
380	FE	D	C	B	AG	F	E	D	CB	A
390	G	F	ED	C	B	A	GF	E	D	C

Century leap years (those divisble by 400) always have dominical letter BA, while exceptional common years (other century years) always have dominical letter C (if the year is 100 mod 400), E (if the year is 200 mod 400), or G (if the year is 300 mod 400).