Current week number today

Updated on by Michael Mühl
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Week Number Calculator

The Week Number Calculator uses a date to calculate the corresponding week number. Conversely, a week number can be used to determine the start and end date of that week. In addition to the international ISO 8601 calculation method, other internationally relevant methods for calculating the week number are supported

Current week number today, May 13, 2021

Week 19

Monday, May 10, 2021 – Sunday, May 16, 2021

The week number

The week number is often used to coordinate appointments or deadlines. The calendar year is divided into sequentially numbered calendar weeks. The year begins at the beginning of January with the first calendar week, continues through the current calendar week and ends at the end of December with week number 52 or 53.

But with which weekday does a week begin? When exactly does the first calendar week begin and what is the number of the current week? How does it look at the end of the year? We will clarify these and other questions for you below.

With which weekday does the week begin?

The official calendar week starts on Monday, as we are used to in terms of working week and school weeks. It ends with Sunday.

When does the first week of the year begin?

This question is somewhat more difficult to answer: In the official calendar week system, the first Thursday of the year must be in the first calendar week. This means that the first week of the year must contain at least four days of the new year and therefore a maximum of three days of the first week can be in the old year.

If January 1st is a Wednesday, the first calendar week starts on Monday, December 30th. This 1st week then contains two days of the old year (Monday and Tuesday) and five days of the new year (Wednesday to Sunday).

However, if January 1 is Friday, the first calendar week does not start until Monday, January 4. The previous week would have contained only three days of the new year (Friday, Saturday, Sunday)

Unlike in some other countries, the 1st week does not necessarily start exactly on January 1st, but usually a few days earlier last year. However, this ensures that each calendar week, i.e. from the first to the current calendar week to the last calendar week, always consists of seven days.

How is the current week number determined?

The current week number is obtained by counting the number of weeks from the first Monday of the first calendar week to the Monday of the current week. The week number today is then identified by the consecutive number and can also be defined by the date of the beginning and end of the week.

Are week numbers internationally regulated?

Yes, week numbers are internationally standardized by ISO 8601. The ISO (International Organization for Standardization) thus provides an international recommendation for the calendar week system, which is generally used especially in Europe and Asia.

Are there other methods for determining the current week number?

Yes, the numbering of the current calendar week is always based on the definition of the first week number, but this can be done differently:

While with the ISO standard the week always begins on Mondays, in North America, most Latin American countries, Australia as well as in Japan, Israel and South Korea it begins on Sundays. In the Arab world, the week begins on Saturday.

While the first week of the ISO standard is partly in the old as well as in the new year, in many other countries the first week - independent of the day of the week - starts exactly on January 1st. This is more intuitive than with the ISO standard, but then the first and last week of the year usually consists of less than seven days.

This can lead to misunderstandings in the case of international appointments, which is why a more precise specification of the current week number based on the current date is advisable in such cases.

Determine current week number with the week number calculator

With the week number calculator you can calculate the respective week not only for the actual week but also for any other date and vice versa determine the respective calendar week using a date.

Source information

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

Last update on May 13, 2021

The pages of the "Week Numbers" category were last editorially reviewed by Michael Mühl on May 13, 2021. They all correspond to the current status.

Previous changes on June 25, 2020