Calendar Week Calculator
Find the calendar week for a date or the date for a calendar week.
Ermitteln Sie die Kalenderwoche (KW) nach ISO 8601 für ein beliebiges Datum.
Kalenderwoche
KW 14 / 2026
Wochentag
Sonntag
Woche (Mo - So)
30.03.2026 - 05.04.2026
Tag im Jahr
Tag 95 von 365
Kalenderwochen im April 2026
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
Frequently Asked Questions
How are calendar weeks (KW) numbered?
According to ISO 8601, calendar week 1 is the week containing the first Thursday of the year. Weeks start on Monday. A year can have 52 or 53 calendar weeks.
Why does the calendar week sometimes differ between countries?
Most European countries use the ISO standard (Monday start, first week contains Jan 4). The US often uses a Sunday-start week where week 1 contains January 1, which can differ by one week.
What is the Calendar Week Calculator?
The calendar week calculator determines the calendar week (CW) of a date or shows all calendar weeks of a year with start and end dates.
How does the Calendar Week Calculator work?
Enter a date. The calculator shows the corresponding calendar week per ISO 8601. Alternatively enter a CW to get the start and end dates of that week.
Key Data and Facts
ISO 8601: CW starts on Monday. CW 1 contains the first Thursday of the year. A year has 52 or 53 calendar weeks.
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