All calendar weeks of the current year and our Week CalculatorUpdated 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|
|CW||Start of the CW||End of the CW||ISO-Name|
|1||Monday, January 4, 2021||Sunday, January 10, 2021||2021‑W01|
|2||Monday, January 11, 2021||Sunday, January 17, 2021||2021‑W02|
|3||Monday, January 18, 2021||Sunday, January 24, 2021||2021‑W03|
|4||Monday, January 25, 2021||Sunday, January 31, 2021||2021‑W04|
|5||Monday, February 1, 2021||Sunday, February 7, 2021||2021‑W05|
|6||Monday, February 8, 2021||Sunday, February 14, 2021||2021‑W06|
|7||Monday, February 15, 2021||Sunday, February 21, 2021||2021‑W07|
|8||Monday, February 22, 2021||Sunday, February 28, 2021||2021‑W08|
|9||Monday, March 1, 2021||Sunday, March 7, 2021||2021‑W09|
|10||Monday, March 8, 2021||Sunday, March 14, 2021||2021‑W10|
|11||Monday, March 15, 2021||Sunday, March 21, 2021||2021‑W11|
|12||Monday, March 22, 2021||Sunday, March 28, 2021||2021‑W12|
|13||Monday, March 29, 2021||Sunday, April 4, 2021||2021‑W13|
|14||Monday, April 5, 2021||Sunday, April 11, 2021||2021‑W14|
|15||Monday, April 12, 2021||Sunday, April 18, 2021||2021‑W15|
|16||Monday, April 19, 2021||Sunday, April 25, 2021||2021‑W16|
|17||Monday, April 26, 2021||Sunday, May 2, 2021||2021‑W17|
|18||Monday, May 3, 2021||Sunday, May 9, 2021||2021‑W18|
|19||Monday, May 10, 2021||Sunday, May 16, 2021||2021‑W19|
|20||Monday, May 17, 2021||Sunday, May 23, 2021||2021‑W20|
|21||Monday, May 24, 2021||Sunday, May 30, 2021||2021‑W21|
|22||Monday, May 31, 2021||Sunday, June 6, 2021||2021‑W22|
|23||Monday, June 7, 2021||Sunday, June 13, 2021||2021‑W23|
|24||Monday, June 14, 2021||Sunday, June 20, 2021||2021‑W24|
|25||Monday, June 21, 2021||Sunday, June 27, 2021||2021‑W25|
|26||Monday, June 28, 2021||Sunday, July 4, 2021||2021‑W26|
|27||Monday, July 5, 2021||Sunday, July 11, 2021||2021‑W27|
|28||Monday, July 12, 2021||Sunday, July 18, 2021||2021‑W28|
|29||Monday, July 19, 2021||Sunday, July 25, 2021||2021‑W29|
|30||Monday, July 26, 2021||Sunday, August 1, 2021||2021‑W30|
|31||Monday, August 2, 2021||Sunday, August 8, 2021||2021‑W31|
|32||Monday, August 9, 2021||Sunday, August 15, 2021||2021‑W32|
|33||Monday, August 16, 2021||Sunday, August 22, 2021||2021‑W33|
|34||Monday, August 23, 2021||Sunday, August 29, 2021||2021‑W34|
|35||Monday, August 30, 2021||Sunday, September 5, 2021||2021‑W35|
|36||Monday, September 6, 2021||Sunday, September 12, 2021||2021‑W36|
|37||Monday, September 13, 2021||Sunday, September 19, 2021||2021‑W37|
|38||Monday, September 20, 2021||Sunday, September 26, 2021||2021‑W38|
|39||Monday, September 27, 2021||Sunday, October 3, 2021||2021‑W39|
|40||Monday, October 4, 2021||Sunday, October 10, 2021||2021‑W40|
|41||Monday, October 11, 2021||Sunday, October 17, 2021||2021‑W41|
|42||Monday, October 18, 2021||Sunday, October 24, 2021||2021‑W42|
|43||Monday, October 25, 2021||Sunday, October 31, 2021||2021‑W43|
|44||Monday, November 1, 2021||Sunday, November 7, 2021||2021‑W44|
|45||Monday, November 8, 2021||Sunday, November 14, 2021||2021‑W45|
|46||Monday, November 15, 2021||Sunday, November 21, 2021||2021‑W46|
|47||Monday, November 22, 2021||Sunday, November 28, 2021||2021‑W47|
|48||Monday, November 29, 2021||Sunday, December 5, 2021||2021‑W48|
|49||Monday, December 6, 2021||Sunday, December 12, 2021||2021‑W49|
|50||Monday, December 13, 2021||Sunday, December 19, 2021||2021‑W50|
|51||Monday, December 20, 2021||Sunday, December 26, 2021||2021‑W51|
|52||Monday, December 27, 2021||Sunday, January 2, 2022||2021‑W52|
|53||2021 does not exist week 53||2021 has only 52 calendar weeks||2021‑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|
|CW||Start of the CW||End of the CW|
|1||Friday, January 1, 2021||Saturday, January 2, 2021|
|2||Sunday, January 3, 2021||Saturday, January 9, 2021|
|3||Sunday, January 10, 2021||Saturday, January 16, 2021|
|4||Sunday, January 17, 2021||Saturday, January 23, 2021|
|5||Sunday, January 24, 2021||Saturday, January 30, 2021|
|6||Sunday, January 31, 2021||Saturday, February 6, 2021|
|7||Sunday, February 7, 2021||Saturday, February 13, 2021|
|8||Sunday, February 14, 2021||Saturday, February 20, 2021|
|9||Sunday, February 21, 2021||Saturday, February 27, 2021|
|10||Sunday, February 28, 2021||Saturday, March 6, 2021|
|11||Sunday, March 7, 2021||Saturday, March 13, 2021|
|12||Sunday, March 14, 2021||Saturday, March 20, 2021|
|13||Sunday, March 21, 2021||Saturday, March 27, 2021|
|14||Sunday, March 28, 2021||Saturday, April 3, 2021|
|15||Sunday, April 4, 2021||Saturday, April 10, 2021|
|16||Sunday, April 11, 2021||Saturday, April 17, 2021|
|17||Sunday, April 18, 2021||Saturday, April 24, 2021|
|18||Sunday, April 25, 2021||Saturday, May 1, 2021|
|19||Sunday, May 2, 2021||Saturday, May 8, 2021|
|20||Sunday, May 9, 2021||Saturday, May 15, 2021|
|21||Sunday, May 16, 2021||Saturday, May 22, 2021|
|22||Sunday, May 23, 2021||Saturday, May 29, 2021|
|23||Sunday, May 30, 2021||Saturday, June 5, 2021|
|24||Sunday, June 6, 2021||Saturday, June 12, 2021|
|25||Sunday, June 13, 2021||Saturday, June 19, 2021|
|26||Sunday, June 20, 2021||Saturday, June 26, 2021|
|27||Sunday, June 27, 2021||Saturday, July 3, 2021|
|28||Sunday, July 4, 2021||Saturday, July 10, 2021|
|29||Sunday, July 11, 2021||Saturday, July 17, 2021|
|30||Sunday, July 18, 2021||Saturday, July 24, 2021|
|31||Sunday, July 25, 2021||Saturday, July 31, 2021|
|32||Sunday, August 1, 2021||Saturday, August 7, 2021|
|33||Sunday, August 8, 2021||Saturday, August 14, 2021|
|34||Sunday, August 15, 2021||Saturday, August 21, 2021|
|35||Sunday, August 22, 2021||Saturday, August 28, 2021|
|36||Sunday, August 29, 2021||Saturday, September 4, 2021|
|37||Sunday, September 5, 2021||Saturday, September 11, 2021|
|38||Sunday, September 12, 2021||Saturday, September 18, 2021|
|39||Sunday, September 19, 2021||Saturday, September 25, 2021|
|40||Sunday, September 26, 2021||Saturday, October 2, 2021|
|41||Sunday, October 3, 2021||Saturday, October 9, 2021|
|42||Sunday, October 10, 2021||Saturday, October 16, 2021|
|43||Sunday, October 17, 2021||Saturday, October 23, 2021|
|44||Sunday, October 24, 2021||Saturday, October 30, 2021|
|45||Sunday, October 31, 2021||Saturday, November 6, 2021|
|46||Sunday, November 7, 2021||Saturday, November 13, 2021|
|47||Sunday, November 14, 2021||Saturday, November 20, 2021|
|48||Sunday, November 21, 2021||Saturday, November 27, 2021|
|49||Sunday, November 28, 2021||Saturday, December 4, 2021|
|50||Sunday, December 5, 2021||Saturday, December 11, 2021|
|51||Sunday, December 12, 2021||Saturday, December 18, 2021|
|52||Sunday, December 19, 2021||Saturday, December 25, 2021|
|53||Sunday, December 26, 2021||Friday, 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.
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.
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.
Please enter the day, i.e., the day of the month for calculating the week number.
Please enter the month for the week number calculation.
Please enter the year for the week number.
Week number entries / calender week
Please enter the week number for the calculation of week start and week end.
Please enter the year of the week number for the calculation of week start and week end.
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.
- 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.
- 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.
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.
More online calculators
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
- Publication of the Week Number Calculator
- Editorial revision of all texts in this category