Week Number & ISO 8601 Formatter
Get ISO week number, day of year, quarter, and convert dates to ISO 8601 format. Parse and format dates in multiple formats.
Enter Date
Week & Calendar Info
ISO Week Number
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Day of Year
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Quarter
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Day of Week
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Leap Year
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ISO 8601 Formats
Date (YYYY-MM-DD)
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Date & Time
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UTC (Z suffix)
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Week Format (YYYY-Www)
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Ordinal (YYYY-DDD)
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Unix Timestamp
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Parse ISO 8601 String
Parsed Date
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Status
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How to Use
1
Enter a Date
Select a date and optionally a time to see week number, day of year, quarter, and ISO 8601 formats.
2
Copy Formats
Click the Copy button next to any ISO 8601 format to copy it to your clipboard.
3
Parse ISO Strings
Paste an ISO 8601 date string to parse it into a human-readable format.
FAQ
What is ISO 8601?
ISO 8601 is an international standard for representing dates and times. The most common format is YYYY-MM-DD (e.g., 2024-12-25).
What is an ISO week number?
ISO weeks start on Monday and week 1 is the week containing the first Thursday of the year. This can differ from calendar weeks in some countries.