Short answer
Week number calculator
Convert a date to an ISO week or a week number to its exact dates.
Calculate a week number
ISO notation
Difference
Add or subtract weeks
Year overview
Inputs are calendar dates without a time. ISO classification is therefore independent of the device time zone.
Short answer
Choose a date or enter an ISO week-year and week number; the result remains shareable in the URL.
How it works
Impossible dates and week 53 in a 52-week year are rejected explicitly.