Day of the Week Calculator
Free online day of the week calculator. Enter any date and instantly find out what day of the week it falls on.
How to Use the Day of the Week Calculator
Enter any date and the tool instantly shows what day of the week it falls on. Additional facts include the day number of the year, ISO week number, and leap year status. Use the birthday section to find what day you were born on.
About This Tool
Find the day of the week for any date — past, present, or future. Also shows the day number of the year, ISO week number, and whether the year is a leap year. Includes a birthday feature that tells you what day of the week you were born on. Great for trivia, event planning, and historical research. See also the Age Calculator and Date Calculator.
Quick Reference Table
| Day | ISO Number |
|---|---|
| Monday | 1 |
| Tuesday | 2 |
| Wednesday | 3 |
| Thursday | 4 |
| Friday | 5 |
| Saturday | 6 |
| Sunday | 7 |
Frequently Asked Questions
How far back in history does this work?
The calculator works for any date supported by the JavaScript Date object, which covers thousands of years in both directions.
What is the ISO week number?
ISO 8601 defines week numbering where Week 1 is the week containing the first Thursday of the year. Weeks start on Monday.
Does this account for calendar changes?
The calculator uses the proleptic Gregorian calendar. For dates before the Gregorian calendar was adopted (1582 in most countries), results follow Gregorian rules rather than the Julian calendar that was in use at the time.