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Week Calculator

Created by Tibor Pál, PhD candidate and Steven Wooding
Reviewed by Steven Wooding
Last updated: Jul 02, 2024

We created the week calculator (or week counter) to help you find the exact number of weeks and days between two given dates. In other words, this simple tool will count weeks from the date you set until the last day of the given period.

In addition, we show which week and day of the week are the set dates.

In the following text, you can read about:

  • How to count weeks between dates;
  • How to use the week calculator; and
  • How many weeks are in a leap year?

In addition, we answer some interesting questions in the FAQ section.

💡 If you are looking to find out the number of days between two dates, head over to our day counter tool. Or if it's the number of months you'd like to know, our month calculator can help.

How do I count weeks between dates?

Follow the below steps to count weeks between dates:

  1. Count the days between the two dates.
  2. Divide the number by 7.
  3. Round down the number to the first integer if you get a decimal.

How to use the number of weeks calculator

To use our week counter tool, you need set the two variables:

  1. Starting day — Date from which you would like to count the weeks.
  2. Last day — Date until which you would like to count the weeks.

After setting the two dates, you can immediately read how many weeks and days are between the two dates.

Note that the starting day is not included in the counting.

In addition, we also show which week and day of the week are the given dates.

For calculating the week number, we use the ISO 8601 standard, which has the following rules:

  • The first day of the week is Monday;

  • Week 1 of a given year is the week containing 4 January;

  • Thursday in the current week decides which year the week is in;

  • Week numbers range from 1 to 53, though most years have 52:

    • 52 × 7 = 364 days — The occasional week 53 covers the 365th day and the 366th day in leap years;
  • Week 1 may start in the last days of the previous year:

    • Week 1 of 2025 starts on Monday, 30 December 2024;
  • The last week (52 or 53) may end during the first days of the following year:

    • Week 52 of 2033 ends on Sunday, 1 January 2034.


What is the first day of the week?

While the International Organization for Standardization (ISO 8601) designates Monday as the beginning of the trade and business week, cultural and historical customs may start the week with another day.

For example, many countries like the U.S., Canada, or China consider Sunday the first day of the week, while other countries in the Middle East begin with Saturday.

How many weeks are in a year?

Depending on the given year, there are 52 weeks in a year plus one or two days. While in an ordinary year which is not a leap year, the number of weeks is 52 plus one day (365 / 7 = 52 weeks + 1 days), leap years contain 52 weeks plus two days (366 / 7 = 52 weeks + 2 days).

Does a year have exactly 52 weeks?

No. Since an ordinary year consists of 365 days and a leap year has 366 days, there are always one or two days addition for the 52 weeks.

Tibor Pál, PhD candidate and Steven Wooding
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