Week Numbers 2020

What Week of the Year Is It
Week numbers of

How many ISO weeks are in 2020?

Answer

had
53 ISO weeks

2020 ended on Thursday, December 31, 2020. Its last ISO week, week 53, ran until Sunday, January 3, 2021.

All 53 ISO weeks of 2020

WeekMondaySunday
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
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53

ISO weeks are always whole, Monday to Sunday, so the numbering of 2020 starts on Monday, December 30, 2019, and ends on Sunday, January 3, 2021. To see these weeks inside the months, open the 2020 calendar with week numbers.

Why 2020 has 53 ISO weeks

53 weeks ⇔ January 1 is a Thursday, or a Wednesday in a leap year

2020 starts on Wednesday, January 1, 2020, and ends on Thursday, December 31, 2020; it is a leap year of 366 days. January 1 is a Wednesday and the year is a leap year, so it has 53 numbered weeks. Week 1 is the week that contains the first Thursday of the year, January 2, 2020.

Counted as whole blocks of seven days inside the calendar year, 2020 is 366 = 52 × 7 + 2, that is 52 weeks and 2 days. Both are true: the numbered ISO weeks are whole, so the first and the last of them may borrow days from the neighbouring years.

In the US numbering (weeks from Sunday, week 1 is the week that contains January 1) 2020 has 52 weeks, and week 1 starts on Sunday, December 29, 2019.

See Also

What Week of the Year Is It

This page tells you the number of the current week in the ISO 8601 system — weeks start on Monday and week 1 is the week with the first Thursday of the year — and in the US system, where weeks start on Sunday. For any year it lists every numbered week with the dates of its Monday and Sunday. For example, it can help you find out how many ISO weeks are in 2020? (The answer is: 53 weeks). Enter a year (e.g. "2026") and hit the "Show" button.

ISO Weeks in Nearby Years

YearISO weeksWeek 1 startsLast week ends
202053Dec 30, 2019Jan 3, 2021
202152Jan 4, 2021Jan 2, 2022
202252Jan 3, 2022Jan 1, 2023
202352Jan 2, 2023Dec 31, 2023
202452Jan 1, 2024Dec 29, 2024
202552Dec 30, 2024Dec 28, 2025
202653Dec 29, 2025Jan 3, 2027
202752Jan 4, 2027Jan 2, 2028
202852Jan 3, 2028Dec 31, 2028
202952Jan 1, 2029Dec 30, 2029
203052Dec 31, 2029Dec 29, 2030

FAQ

How many ISO weeks are in 2020?

2020 had 53 ISO weeks

When does week 1 of 2020 start?

Week 1 of 2020 runs from Monday, December 30, 2019, to Sunday, January 5, 2020. It is the week that contains the first Thursday of the year, January 2, 2020.

When does the last week of 2020 end?

The last ISO week of 2020 is week 53: Monday, December 28, 2020, to Sunday, January 3, 2021.

Why does 2020 have 53 ISO weeks?

2020 starts on a Wednesday and ends on a Thursday, and it is a leap year of 366 days. A year has 53 ISO weeks when 1 January is a Thursday, or a Wednesday in a leap year — here it is a Wednesday, and the year is a leap year.