Current ISO Week Number
Today’s ISO-8601 week number is shown at the top, using your device’s date. Weeks start on Monday, and week 1 is the week with the year’s first Thursday. Pick any other date below to get its week and week-year.
Week number for any date
Pick a date to get its ISO-8601 week number, week-year and Monday–Sunday range.
This week (ISO)
Week …
Reading today’s date from your device…
Need day counts? Use the date calculator or days until.
What the ISO week number is
The page returns the ISO-8601 week number and the week-year for the date you pick. Weeks start on Monday. Week 1 is the week that contains the year’s first Thursday, which is the same rule as “the week that contains 4 January”.
The week-year can differ from the calendar year. 1 January can fall in week 52 or 53 of the previous week-year. Late December can fall in week 1 of the next week-year. Reports that say “week 1” should say which week-year they mean.
How to use it
- Pick a calendar date. The result updates from that date.
- Read the week number and the week-year together.
- If you are matching a payroll or school calendar, confirm they use ISO weeks and not a Sunday-start local week.
- For the number of days until that date, open Days Until.
The date stays in the browser. It is not uploaded.
Questions
Do weeks start on Sunday?
Why is the week-year not the same as the calendar year?
Is week 53 an error?
Frequently Asked Questions
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