How many weeks in a year?

Any impatient soul counting down to their next birthday, annual holiday or festival is going to need 52 weeks’ worth of patience, because that’s the length of a complete year.

A normal year in the ‘modern’ calendar has 365 days, which, when divided by 7 (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday) equals 52.1428571 weeks.

Every four years, there is a leap year*, adding an extra day into the calendar (pity those 17 year olds born on February 29th 2000, who have only had 4 true birthdays). In this case, the calculation is 366 divided by 7, which equals 52.2857, so it’s still just 52 weeks.

This is all based upon the Gregorian calendar (introduced back in 1582), which cycles every 400 years. If you want to go a step further and work out the average number of weeks in a year across the full Gregorian calendar, you’ll find that a year works out at 365.2425 days. When divided by 7 it gives you a total of 52.1775 weeks.

Summary of years

Year type Number of days Number of weeks Comments
Lunar 354.37 50.6242857 Muslim calendar year
Common year 365 52.1428571
Gregorian (average) 365.2425 52.1775
Julian 365.25 52.1785714 used in astronomy (computing the distance covered by a light-year, etc)
Leap year 366 52.2857143

Here’s a table to show you how common years from the Gregorian calendar are broken down into weeks and days:

Weeks in a year table

Year Number of weeks Number of days Leap year?
2015 52 weeks and 1 day 365
2016 52 weeks and 2 days 366 yes
2017 52 weeks and 1 day 365
2018 52 weeks and 1 day 365
2019 52 weeks and 1 day 365
2020 52 weeks and 2 days 366 yes
2021 52 weeks and 1 day 365
2022 52 weeks and 1 day 365
2023 52 weeks and 1 day 365
2024 52 weeks and 2 days 366 yes
2025 52 weeks and 1 day 365

The exception to the “52 weeks” rule pops up if you’re using a fancy academic journal or office wall planner; sometimes they number the weeks based on them running from Sunday to Saturday, or Monday to Sunday, breaking up the first and last weeks of the year to fit this mould. Although there are still only 52 weeks in the year, and time doesn’t magically slow down**, the way a calendar like that counts fragments at the start and end of the year might mean that the weeks are numbered as high as 54. E.g.:

  • WEEK 1: Thursday 1 January, Friday 2 January, Saturday 3 January, Sunday 4 January
  • WEEK 2: Monday 5 January, Tuesday 6 January….

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