Date-to-Weekday Finder
Enter any date to find out what day of the week it falls on.
Frequently asked questions
What do "Day of Year" and "ISO Week" mean?
Day of Year is how many days have passed since the start of that year (January 1st is Day 1). ISO Week follows the international ISO-8601 standard, where weeks start on Monday and week 1 is the week containing the year's first Thursday — this can occasionally place late-December or early-January dates in a different "week-numbering year" than their calendar year, which is why both are shown together.
Is this accurate for dates before 1582?
This tool uses the modern Gregorian calendar projected backward (a "proleptic" calendar), which is standard for computer date calculations. Many countries didn't actually adopt the Gregorian calendar until 1582 or later, so for historical dates before your country's adoption date, the weekday shown may not match what a calendar from that time period would have said.
How far back or forward can I calculate?
Essentially any date from the year 1 to the year 9999, the practical range supported by the date field.