Norway uses ISO 8601 week numbers. Weeks start on Monday, and week 1 is the week that contains 4 January, which is the week with the year's first Thursday. So 29–31 December can fall in week 1 of the next year, and 1–3 January in week 52 or 53 of the last. Some years, like 2026, have 53 weeks.
About week numbers
Norway numbers weeks by the international standard ISO 8601. Weeks run from Monday to Sunday, and week 1 is the week that contains 4 January — which is the same as the week that holds the year's first Thursday. Week numbers are everywhere in Norwegian working life and school: holidays, delivery dates, project plans and rotas are often given as a week rather than a date.
Because a week belongs to the year its Thursday falls in, the days around New Year can belong to the neighbouring year. 29, 30 and 31 December can be in week 1 of the next year, and 1, 2 and 3 January can be in week 52 or 53 of the one before. That's why a year sometimes has 53 weeks: when 1 January is a Thursday, or a Wednesday in a leap year, the year contains 53 Thursdays.
This week's number is worked out from the date on your own device, so it's right wherever you are. The table lists every week of the year you pick, with the Monday it starts and the Sunday it ends, and marks the current week.
How to use the calculator
1
See this week's number
It's at the top, with the dates from Monday to Sunday and how many weeks the year has.
2
Look up any date
Pick a date to see which week it falls in — useful for birthdays, deadlines and the days around New Year.
3
Browse a whole year
Use the arrows or type a year between 1900 and 2100 to list every week with its dates.
Frequently asked questions
What week is it now?
The number at the top of this page is the current week, worked out from the date on your device. Norway uses ISO 8601 week numbers: weeks start on Monday, and week 1 is the week with 4 January in it.
Which years have 53 weeks?
A year has 53 weeks when 1 January is a Thursday, or a Wednesday in a leap year. Between 2020 and 2050 that is 2020, 2026, 2032, 2037, 2043 and 2048. In those years week 53 ends on the first Sunday of January.
When does week 1 start?
On the Monday of the week that contains 4 January. That Monday is always between 29 December and 4 January, so week 1 can start in the old year.
Why does 1 January sometimes belong to week 52 or 53?
A week belongs to the year its Thursday falls in. When 1 January is a Friday, Saturday or Sunday, that week's Thursday is in December, so the week is the last one of the previous year, and week 1 starts on the following Monday.
Do all countries number weeks the same way?
No. Most of Europe uses ISO 8601 like Norway, but calendars made for the United States often start weeks on Sunday and count the week with 1 January in it as week 1, so their numbers can be one off from Norwegian ones around New Year and in some years all year.
How do I get the week number in Excel or Google Sheets?
Use =ISOWEEKNUM(A1), which returns the ISO week number in Excel 2013 and later and in Google Sheets. WEEKNUM without a second argument starts weeks on Sunday and counts from 1 January, which doesn't match Norwegian calendars; WEEKNUM(A1, 21) gives the ISO number. A Norwegian-language Excel shows the functions under translated names.