Week Number Lookup
Looks up the ISO 8601 week number of any date, along with the US week numbering, the day of the year, and the date range covered by that week. Also shows how many ISO weeks the year has (52 or 53).
Read the full guide to this tool
Notes
- ISO weeks start on Monday and week 1 is the week containing the first Thursday of the year, so Jan 1 can belong to week 52 or 53 of the previous year.
- Everything runs locally in your browser; nothing you enter is sent to any server.
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