Week Number Calculator

Calendar weeks 2021 - CW 2021

Week Numbers ﹣ Calendar weeks 2021

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
CW Mo Tu We Th Fr Sa SuISO-Name
CW 1 04/01 05/01 06/01 07/01 08/01 09/01 10/012021‑W01
CW 2 11/01 12/01 13/01 14/01 15/01 16/01 17/012021‑W02
CW 3 18/01 19/01 20/01 21/01 22/01 23/01 24/012021‑W03
CW 4 25/01 26/01 27/01 28/01 29/01 30/01 31/012021‑W04
CW 5 01/02 02/02 03/02 04/02 05/02 06/02 07/022021‑W05
CW 6 08/02 09/02 10/02 11/02 12/02 13/02 14/022021‑W06
CW 7 15/02 16/02 17/02 18/02 19/02 20/02 21/022021‑W07
CW 8 22/02 23/02 24/02 25/02 26/02 27/02 28/022021‑W08
CW 9 01/03 02/03 03/03 04/03 05/03 06/03 07/032021‑W09
CW 10 08/03 09/03 10/03 11/03 12/03 13/03 14/032021‑W10
CW 11 15/03 16/03 17/03 18/03 19/03 20/03 21/032021‑W11
CW 12 22/03 23/03 24/03 25/03 26/03 27/03 28/032021‑W12
CW 13 29/03 30/03 31/03 01/04 02/04 03/04 04/042021‑W13
CW 14 05/04 06/04 07/04 08/04 09/04 10/04 11/042021‑W14
CW 15 12/04 13/04 14/04 15/04 16/04 17/04 18/042021‑W15
CW 16 19/04 20/04 21/04 22/04 23/04 24/04 25/042021‑W16
CW 17 26/04 27/04 28/04 29/04 30/04 01/05 02/052021‑W17
CW 18 03/05 04/05 05/05 06/05 07/05 08/05 09/052021‑W18
CW 19 10/05 11/05 12/05 13/05 14/05 15/05 16/052021‑W19
CW 20 17/05 18/05 19/05 20/05 21/05 22/05 23/052021‑W20
CW 21 24/05 25/05 26/05 27/05 28/05 29/05 30/052021‑W21
CW 22 31/05 01/06 02/06 03/06 04/06 05/06 06/062021‑W22
CW 23 07/06 08/06 09/06 10/06 11/06 12/06 13/062021‑W23
CW 24 14/06 15/06 16/06 17/06 18/06 19/06 20/062021‑W24
CW 25 21/06 22/06 23/06 24/06 25/06 26/06 27/062021‑W25
CW 26 28/06 29/06 30/06 01/07 02/07 03/07 04/072021‑W26
CW 27 05/07 06/07 07/07 08/07 09/07 10/07 11/072021‑W27
CW 28 12/07 13/07 14/07 15/07 16/07 17/07 18/072021‑W28
CW 29 19/07 20/07 21/07 22/07 23/07 24/07 25/072021‑W29
CW 30 26/07 27/07 28/07 29/07 30/07 31/07 01/082021‑W30
CW 31 02/08 03/08 04/08 05/08 06/08 07/08 08/082021‑W31
CW 32 09/08 10/08 11/08 12/08 13/08 14/08 15/082021‑W32
CW 33 16/08 17/08 18/08 19/08 20/08 21/08 22/082021‑W33
CW 34 23/08 24/08 25/08 26/08 27/08 28/08 29/082021‑W34
CW 35 30/08 31/08 01/09 02/09 03/09 04/09 05/092021‑W35
CW 36 06/09 07/09 08/09 09/09 10/09 11/09 12/092021‑W36
CW 37 13/09 14/09 15/09 16/09 17/09 18/09 19/092021‑W37
CW 38 20/09 21/09 22/09 23/09 24/09 25/09 26/092021‑W38
CW 39 27/09 28/09 29/09 30/09 01/10 02/10 03/102021‑W39
CW 40 04/10 05/10 06/10 07/10 08/10 09/10 10/102021‑W40
CW 41 11/10 12/10 13/10 14/10 15/10 16/10 17/102021‑W41
CW 42 18/10 19/10 20/10 21/10 22/10 23/10 24/102021‑W42
CW 43 25/10 26/10 27/10 28/10 29/10 30/10 31/102021‑W43
CW 44 01/11 02/11 03/11 04/11 05/11 06/11 07/112021‑W44
CW 45 08/11 09/11 10/11 11/11 12/11 13/11 14/112021‑W45
CW 46 15/11 16/11 17/11 18/11 19/11 20/11 21/112021‑W46
CW 47 22/11 23/11 24/11 25/11 26/11 27/11 28/112021‑W47
CW 48 29/11 30/11 01/12 02/12 03/12 04/12 05/122021‑W48
CW 49 06/12 07/12 08/12 09/12 10/12 11/12 12/122021‑W49
CW 50 13/12 14/12 15/12 16/12 17/12 18/12 19/122021‑W50
CW 51 20/12 21/12 22/12 23/12 24/12 25/12 26/122021‑W51
CW 52 27/12 28/12 29/12 30/12 31/12 01/01 02/012021‑W52
CW 53 2021 does not exist week 53. 2021 has only 52 calendar weeks.

The ISO calendar weeks for 2021 are defined according to the international ISO standard. That is, each calendar week starts on Monday and ends on Sunday. Even during the change of year, a new calendar week starts on Monday and ends on Sunday. The ISO standard specifies that the majority of the first calendar week (i.e., at least four days) must lie in the new year.

Table of all American calendar weeks for 2021

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
CW Su Mo Tu We Th Fr Sa
CW 101/0102/01
CW 2 03/01 04/01 05/01 06/01 07/01 08/01 09/01
CW 3 10/01 11/01 12/01 13/01 14/01 15/01 16/01
CW 4 17/01 18/01 19/01 20/01 21/01 22/01 23/01
CW 5 24/01 25/01 26/01 27/01 28/01 29/01 30/01
CW 6 31/01 01/02 02/02 03/02 04/02 05/02 06/02
CW 7 07/02 08/02 09/02 10/02 11/02 12/02 13/02
CW 8 14/02 15/02 16/02 17/02 18/02 19/02 20/02
CW 9 21/02 22/02 23/02 24/02 25/02 26/02 27/02
CW 10 28/02 01/03 02/03 03/03 04/03 05/03 06/03
CW 11 07/03 08/03 09/03 10/03 11/03 12/03 13/03
CW 12 14/03 15/03 16/03 17/03 18/03 19/03 20/03
CW 13 21/03 22/03 23/03 24/03 25/03 26/03 27/03
CW 14 28/03 29/03 30/03 31/03 01/04 02/04 03/04
CW 15 04/04 05/04 06/04 07/04 08/04 09/04 10/04
CW 16 11/04 12/04 13/04 14/04 15/04 16/04 17/04
CW 17 18/04 19/04 20/04 21/04 22/04 23/04 24/04
CW 18 25/04 26/04 27/04 28/04 29/04 30/04 01/05
CW 19 02/05 03/05 04/05 05/05 06/05 07/05 08/05
CW 20 09/05 10/05 11/05 12/05 13/05 14/05 15/05
CW 21 16/05 17/05 18/05 19/05 20/05 21/05 22/05
CW 22 23/05 24/05 25/05 26/05 27/05 28/05 29/05
CW 23 30/05 31/05 01/06 02/06 03/06 04/06 05/06
CW 24 06/06 07/06 08/06 09/06 10/06 11/06 12/06
CW 25 13/06 14/06 15/06 16/06 17/06 18/06 19/06
CW 26 20/06 21/06 22/06 23/06 24/06 25/06 26/06
CW 27 27/06 28/06 29/06 30/06 01/07 02/07 03/07
CW 28 04/07 05/07 06/07 07/07 08/07 09/07 10/07
CW 29 11/07 12/07 13/07 14/07 15/07 16/07 17/07
CW 30 18/07 19/07 20/07 21/07 22/07 23/07 24/07
CW 31 25/07 26/07 27/07 28/07 29/07 30/07 31/07
CW 32 01/08 02/08 03/08 04/08 05/08 06/08 07/08
CW 33 08/08 09/08 10/08 11/08 12/08 13/08 14/08
CW 34 15/08 16/08 17/08 18/08 19/08 20/08 21/08
CW 35 22/08 23/08 24/08 25/08 26/08 27/08 28/08
CW 36 29/08 30/08 31/08 01/09 02/09 03/09 04/09
CW 37 05/09 06/09 07/09 08/09 09/09 10/09 11/09
CW 38 12/09 13/09 14/09 15/09 16/09 17/09 18/09
CW 39 19/09 20/09 21/09 22/09 23/09 24/09 25/09
CW 40 26/09 27/09 28/09 29/09 30/09 01/10 02/10
CW 41 03/10 04/10 05/10 06/10 07/10 08/10 09/10
CW 42 10/10 11/10 12/10 13/10 14/10 15/10 16/10
CW 43 17/10 18/10 19/10 20/10 21/10 22/10 23/10
CW 44 24/10 25/10 26/10 27/10 28/10 29/10 30/10
CW 45 31/10 31/10 01/11 02/11 03/11 04/11 05/11
CW 46 07/11 08/11 09/11 10/11 11/11 12/11 13/11
CW 47 14/11 15/11 16/11 17/11 18/11 19/11 20/11
CW 48 21/11 22/11 23/11 24/11 25/11 26/11 27/11
CW 49 28/11 29/11 30/11 01/12 02/12 03/12 04/12
CW 50 05/12 06/12 07/12 08/12 09/12 10/12 11/12
CW 51 12/12 13/12 14/12 15/12 16/12 17/12 18/12
CW 52 19/12 20/12 21/12 22/12 23/12 24/12 25/12
CW 5326/1227/1228/1229/1230/1231/12

The "American" calendar weeks for 2021 are used in the USA, Canada and most Latin American countries, Australia, Japan, Israel, South Korea and others. Unlike the otherwise internationally standardised ISO weeks, the American calendar weeks start on Sundays instead of Mondays and end on Saturdays. However, the first calendar week always begins on the 1st of January and the last always ends on the 31st of December. These two weeks can have fewer than seven days. There are always 53 calendar weeks, except in a leap year where 31st December is a Sunday. As a result, such a year will have 54 calendar weeks.

Calculation of any calendar weeks 2021

Source information

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

Last update on March 20, 2023

The pages of the 'Week Numbers' category were last editorially reviewed by Michael Mühl on March 20, 2023. They all correspond to the current status.

Previous changes on June 25, 2021