Week numbers for 2021

What is a week number?

A week number is the sequential number assigned to each week in a calendar year. We use the ISO 8601 international standard, where each week begins on Monday and runs through Sunday.

Calendar with week numbers

The calendar consists of 12 months. To reference smaller time periods, week numbers provide a convenient solution. Many activities are scheduled for a specific week when an exact date isn't yet confirmed. Week numbers offer a practical way to communicate these timeframes.

Week numbers for 2021

Every week runs from Monday to Sunday. Week 1 is the week with the first Thursday of January, following the ISO 8601 standard used in business, logistics and most of the world outside the US.

The current week number is determined by the date. January 4 always falls in the first week of the year - this is the standard rule. Because of this, February 1 always falls in week 5.

You can calculate the current week number yourself by counting the elapsed weeks or checking a calendar. However, this is time-consuming, which is why we provide a complete overview for each year showing all week numbers with their start and end dates.

What is the week number this week?

Week numbers are particularly important for maintaining organized schedules and coordinating with others. Our tools make it easy to track week numbers throughout the year.