All calendar weeks of the current year and our Week Calculator

Updated on by Michael Mühl

Table with all current European and Asian ISO calendar weeks

The following table shows all ISO calendar weeks 2021 from 1 to 53, with their start date beginning on Monday and their end date falling on Sunday.

European and Asian ISO calendar weeks 2021 - CW 2021
CWStart of the CWEnd of the CWISO-Name
1Monday, January 4, 2021Sunday, January 10, 20212021‑W01
2Monday, January 11, 2021Sunday, January 17, 20212021‑W02
3Monday, January 18, 2021Sunday, January 24, 20212021‑W03
4Monday, January 25, 2021Sunday, January 31, 20212021‑W04
5Monday, February 1, 2021Sunday, February 7, 20212021‑W05
6Monday, February 8, 2021Sunday, February 14, 20212021‑W06
7Monday, February 15, 2021Sunday, February 21, 20212021‑W07
8Monday, February 22, 2021Sunday, February 28, 20212021‑W08
9Monday, March 1, 2021Sunday, March 7, 20212021‑W09
10Monday, March 8, 2021Sunday, March 14, 20212021‑W10
11Monday, March 15, 2021Sunday, March 21, 20212021‑W11
12Monday, March 22, 2021Sunday, March 28, 20212021‑W12
13Monday, March 29, 2021Sunday, April 4, 20212021‑W13
14Monday, April 5, 2021Sunday, April 11, 20212021‑W14
15Monday, April 12, 2021Sunday, April 18, 20212021‑W15
16Monday, April 19, 2021Sunday, April 25, 20212021‑W16
17Monday, April 26, 2021Sunday, May 2, 20212021‑W17
18Monday, May 3, 2021Sunday, May 9, 20212021‑W18
19Monday, May 10, 2021Sunday, May 16, 20212021‑W19
20Monday, May 17, 2021Sunday, May 23, 20212021‑W20
21Monday, May 24, 2021Sunday, May 30, 20212021‑W21
22Monday, May 31, 2021Sunday, June 6, 20212021‑W22
23Monday, June 7, 2021Sunday, June 13, 20212021‑W23
24Monday, June 14, 2021Sunday, June 20, 20212021‑W24
25Monday, June 21, 2021Sunday, June 27, 20212021‑W25
26Monday, June 28, 2021Sunday, July 4, 20212021‑W26
27Monday, July 5, 2021Sunday, July 11, 20212021‑W27
28Monday, July 12, 2021Sunday, July 18, 20212021‑W28
29Monday, July 19, 2021Sunday, July 25, 20212021‑W29
30Monday, July 26, 2021Sunday, August 1, 20212021‑W30
31Monday, August 2, 2021Sunday, August 8, 20212021‑W31
32Monday, August 9, 2021Sunday, August 15, 20212021‑W32
33Monday, August 16, 2021Sunday, August 22, 20212021‑W33
34Monday, August 23, 2021Sunday, August 29, 20212021‑W34
35Monday, August 30, 2021Sunday, September 5, 20212021‑W35
36Monday, September 6, 2021Sunday, September 12, 20212021‑W36
37Monday, September 13, 2021Sunday, September 19, 20212021‑W37
38Monday, September 20, 2021Sunday, September 26, 20212021‑W38
39Monday, September 27, 2021Sunday, October 3, 20212021‑W39
40Monday, October 4, 2021Sunday, October 10, 20212021‑W40
41Monday, October 11, 2021Sunday, October 17, 20212021‑W41
42Monday, October 18, 2021Sunday, October 24, 20212021‑W42
43Monday, October 25, 2021Sunday, October 31, 20212021‑W43
44Monday, November 1, 2021Sunday, November 7, 20212021‑W44
45Monday, November 8, 2021Sunday, November 14, 20212021‑W45
46Monday, November 15, 2021Sunday, November 21, 20212021‑W46
47Monday, November 22, 2021Sunday, November 28, 20212021‑W47
48Monday, November 29, 2021Sunday, December 5, 20212021‑W48
49Monday, December 6, 2021Sunday, December 12, 20212021‑W49
50Monday, December 13, 2021Sunday, December 19, 20212021‑W50
51Monday, December 20, 2021Sunday, December 26, 20212021‑W51
52Monday, December 27, 2021Sunday, January 2, 20222021‑W52
532021 does not exist week 532021 has only 52 calendar weeks2021‑W53

See below for more on the calculation method of the ISO calendar weeks.

Table of all current American calendar weeks

The following table shows all "American" calendar weeks 2021, with their start date beginning on Sunday and their end date falling on Saturday.

American calendar weeks 2021 - CW 2021
CWStart of the CWEnd of the CW
1Friday, January 1, 2021Saturday, January 2, 2021
2Sunday, January 3, 2021Saturday, January 9, 2021
3Sunday, January 10, 2021Saturday, January 16, 2021
4Sunday, January 17, 2021Saturday, January 23, 2021
5Sunday, January 24, 2021Saturday, January 30, 2021
6Sunday, January 31, 2021Saturday, February 6, 2021
7Sunday, February 7, 2021Saturday, February 13, 2021
8Sunday, February 14, 2021Saturday, February 20, 2021
9Sunday, February 21, 2021Saturday, February 27, 2021
10Sunday, February 28, 2021Saturday, March 6, 2021
11Sunday, March 7, 2021Saturday, March 13, 2021
12Sunday, March 14, 2021Saturday, March 20, 2021
13Sunday, March 21, 2021Saturday, March 27, 2021
14Sunday, March 28, 2021Saturday, April 3, 2021
15Sunday, April 4, 2021Saturday, April 10, 2021
16Sunday, April 11, 2021Saturday, April 17, 2021
17Sunday, April 18, 2021Saturday, April 24, 2021
18Sunday, April 25, 2021Saturday, May 1, 2021
19Sunday, May 2, 2021Saturday, May 8, 2021
20Sunday, May 9, 2021Saturday, May 15, 2021
21Sunday, May 16, 2021Saturday, May 22, 2021
22Sunday, May 23, 2021Saturday, May 29, 2021
23Sunday, May 30, 2021Saturday, June 5, 2021
24Sunday, June 6, 2021Saturday, June 12, 2021
25Sunday, June 13, 2021Saturday, June 19, 2021
26Sunday, June 20, 2021Saturday, June 26, 2021
27Sunday, June 27, 2021Saturday, July 3, 2021
28Sunday, July 4, 2021Saturday, July 10, 2021
29Sunday, July 11, 2021Saturday, July 17, 2021
30Sunday, July 18, 2021Saturday, July 24, 2021
31Sunday, July 25, 2021Saturday, July 31, 2021
32Sunday, August 1, 2021Saturday, August 7, 2021
33Sunday, August 8, 2021Saturday, August 14, 2021
34Sunday, August 15, 2021Saturday, August 21, 2021
35Sunday, August 22, 2021Saturday, August 28, 2021
36Sunday, August 29, 2021Saturday, September 4, 2021
37Sunday, September 5, 2021Saturday, September 11, 2021
38Sunday, September 12, 2021Saturday, September 18, 2021
39Sunday, September 19, 2021Saturday, September 25, 2021
40Sunday, September 26, 2021Saturday, October 2, 2021
41Sunday, October 3, 2021Saturday, October 9, 2021
42Sunday, October 10, 2021Saturday, October 16, 2021
43Sunday, October 17, 2021Saturday, October 23, 2021
44Sunday, October 24, 2021Saturday, October 30, 2021
45Sunday, October 31, 2021Saturday, November 6, 2021
46Sunday, November 7, 2021Saturday, November 13, 2021
47Sunday, November 14, 2021Saturday, November 20, 2021
48Sunday, November 21, 2021Saturday, November 27, 2021
49Sunday, November 28, 2021Saturday, December 4, 2021
50Sunday, December 5, 2021Saturday, December 11, 2021
51Sunday, December 12, 2021Saturday, December 18, 2021
52Sunday, December 19, 2021Saturday, December 25, 2021
53Sunday, December 26, 2021Friday, December 31, 2021

See below for more on the calculation method of American calendar weeks.

Calendar Week Calculator

With the Calendar Week Calculator, you can use a date to calculate the corresponding calendar week. Conversely, you can use the calendar week to determine the date of the beginning and end of the week you are looking for. You can use the international ISO 8601 calculation method for Europe and Asia and the American calculation method for calendar weeks as the internationally relevant method for calculating calendar weeks.


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More information on the current calendar week

On the special page Current Calendar Week, you will always find the currently valid calendar week. In the navigation, you can select each individual calendar week or, for example, all historical calendar weeks 2020 or select the very latest calendar weeks 2021.

Tips for making entries in the Week Number Calculator

Depending on the selection made in the input of the calculator, different input fields open, which we describe in the following.

Calculation of

Please select the value that you want to calculate. After selecting "Week number", the week number is calculated for the entered date. After selecting the "start and end of a week number" the start and end date for the entered week number are calculated.

Date input

Day

Please enter the day, i.e., the day of the month for calculating the week number.

Month

Please enter the month for the week number calculation.

Year

Please enter the year for the week number.

Week number entries / calender week

Week number

Please enter the week number for the calculation of week start and week end.

Year

Please enter the year of the week number for the calculation of week start and week end.

Calculation method

Select the method of week number calculation. Available are "International according to ISO", "North American calculation" and the "Arabic calculation", which are described in detail below.

Calculation methods supported by the Week Number Calculator

International calculation according to ISO

The international ISO 8601 definition of a week is mainly used in European and Asian countries to number weeks:

Weeks start on a Monday and the first week of the year includes 4th of January. This means that up to three days from the previous year may be included in the first week of the current year and up to three days from the current year may be included in the last week of the previous year.

In other words:

  • The first calendar week of a year is the week containing at least four days of the new year.
  • The first calendar week of a year is the week that contains the first Thursday of January.

Two examples of the first week number according to ISO 8601

  • If 1st of January falls on a Wednesday, the first calendar week begins on Monday, 30th December. This first week then contains two days of the old year (Monday and Tuesday) and five days of the new year (Wednesday to Sunday).
  • However, if 1st of January falls on a Friday, the first calendar week starts on Monday, 4th January. This is because the previous week would have contained only three days of the new year (Friday, Saturday, Sunday)

North American calculation of week numbers

In the USA, Canada and most Latin American countries, Australia as well as in Japan, Israel, South Korea and others, a different system is used for numbering weeks.

In contrast to the ISO standard, Sunday is the first day of the week, which then ends with Saturday. In addition, the first calendar week - regardless of the day of the week - always begins on 1st January.

In other words:

  • The first week of a year always starts on 1st of January and ends on the following Saturday.
  • The last week of a year always begins on the last Sunday of the year and ends on 31st December.

Two examples

  • If 1st of January falls on a Wednesday, the first week of the year starts with this Wednesday and consists of four days (Wednesday, Thursday, Friday and Saturday).
  • If 31st December falls on a Tuesday, the last week of the year begins on Sunday, 29th December and consists of three days (Sunday, Monday and Tuesday).

The rule that the first week always begins on 1st of January is more intuitive than in the ISO standard, as the last calendar week always ends with the final week of the year, and the first week always begins with the new year. However, at the turn of the year, there are usually partial weeks of less than seven days, whereas the ISO calendar weeks always consist of whole weeks.

Arabic calculation of week numbers

In the Arab countries, the system for the numbering of weeks is similar to the North American calculation method just described. However, in contrast to this, Saturday, instead of Sunday, is the start of the week. Thus, the week ends on Friday. Apart from that, the first calendar week always starts on 1st of January here as well, regardless of the weekday.

In other words:

  • The first calendar week of a year always starts on 1st January and ends on the following Friday.
  • The last calendar week of a year always begins on the last Saturday of the year and ends on 31st December.

Two examples

  • If 1st of January falls on a Wednesday, the first calendar week starts with this Wednesday and consists of three days (Wednesday, Thursday and Friday).
  • If 31st December falls on a Tuesday, the last calendar week begins on Saturday, 28th December and consists of four days (Saturday, Sunday, Monday and Tuesday).

With the Arabic calculation method as well, the rule that the first week always begins with 1st of January is more intuitive than with the ISO standard, where the last week always ends in the current year and the first week begins with the new year. Likewise, at the turn of the year, there are usually partial weeks of less than seven days, while the ISO calendar weeks continue to consist of whole weeks.

Different definitions

There are many other definitions for numbering weeks.

In some companies, the first week begins in the middle of the year in order to accurately reflect their financial year, which differs from the calendar year.

In the USA, the week starts predominantly with Sunday, but sometimes the start of the first week of the year is defined as in the ISO 8601 definition, i.e., not on 1st of January.

Since the numbering of calendar weeks is not very common in the USA, the counting method used in the calculator was chosen to reflect the way people speak in casual conversation:

"Week one is the first week of the year, and it starts on 1st of January. The weeks are then numbered sequentially, with each following week starting on Sunday.

Source information

As source for the information in the "Week Numbers" category, we have used in particular:

Last update on September 22, 2021

The pages of the "Week Numbers" category were last editorially reviewed by Michael Mühl on September 22, 2021. They all correspond to the current status.

Previous changes on June 25, 2020