2027 has 365 days, 261 of them working days, across 52 ISO weeks. The number down the left of each month is the ISO week.
January31 days, 21 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
53
28
29
30
31
1
2
3
1
4
5
6
7
8
9
10
2
11
12
13
14
15
16
17
3
18
19
20
21
22
23
24
4
25
26
27
28
29
30
31
February28 days, 20 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
5
1
2
3
4
5
6
7
6
8
9
10
11
12
13
14
7
15
16
17
18
19
20
21
8
22
23
24
25
26
27
28
March31 days, 23 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
9
1
2
3
4
5
6
7
10
8
9
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
1
2
3
4
April30 days, 22 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
13
29
30
31
1
2
3
4
14
5
6
7
8
9
10
11
15
12
13
14
15
16
17
18
16
19
20
21
22
23
24
25
17
26
27
28
29
30
1
2
May31 days, 21 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
17
26
27
28
29
30
1
2
18
3
4
5
6
7
8
9
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
1
2
3
4
5
6
June30 days, 22 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
22
31
1
2
3
4
5
6
23
7
8
9
10
11
12
13
24
14
15
16
17
18
19
20
25
21
22
23
24
25
26
27
26
28
29
30
1
2
3
4
July31 days, 22 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
26
28
29
30
1
2
3
4
27
5
6
7
8
9
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
1
August31 days, 22 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
30
26
27
28
29
30
31
1
31
2
3
4
5
6
7
8
32
9
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
1
2
3
4
5
September30 days, 22 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
35
30
31
1
2
3
4
5
36
6
7
8
9
10
11
12
37
13
14
15
16
17
18
19
38
20
21
22
23
24
25
26
39
27
28
29
30
1
2
3
October31 days, 21 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
39
27
28
29
30
1
2
3
40
4
5
6
7
8
9
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
November30 days, 22 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
44
1
2
3
4
5
6
7
45
8
9
10
11
12
13
14
46
15
16
17
18
19
20
21
47
22
23
24
25
26
27
28
48
29
30
1
2
3
4
5
December31 days, 23 working
wk
Mo
Tu
We
Th
Fr
Sa
Su
48
29
30
1
2
3
4
5
49
6
7
8
9
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
1
2
What the week numbers mean
These are ISO 8601 weeks: every week runs Monday to Sunday and belongs to the year that owns its Thursday. It is why 1 January 2027 falls in week 53 of 2026, and why a year has 53 weeks whenever it starts on a Thursday or is a leap year starting on a Wednesday. The US business convention of numbering from 1 January gives different answers, and payroll systems disagree about which one they mean.