Day of the week calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- The weekday follows from counting days from a known date; days repeat in a 7-day cycle.
- ISO weeks start on Monday and week 1 is the week containing the first Thursday of the year.
| Inputs | Answer |
|---|---|
| Date: 2026-12-25 | Friday, December 25, 2026 is a Friday, day 359 of the year, in ISO week 52. |
| Date: 2000-01-01 | Saturday, January 1, 2000 is a Saturday, day 1 of the year, in ISO week 52. |
| Date: 2028-02-29 | Tuesday, February 29, 2028 is a Tuesday, day 60 of the year, in ISO week 9. |
How to use it
Enter any date to see its weekday, the day of the year, the ISO week number, whether the year is a leap year and how many days remain. Weekdays follow a seven-day cycle, so the calculator counts days from a known date.
ISO weeks start on Monday and week 1 is the week containing the first Thursday of the year.
Frequently asked questions
What day of the week was I born?
Enter your birth date.
What day is 25 December 2026?
A Friday.
What is a leap year?
A year divisible by 4, except century years not divisible by 400.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
About · How we verify this · Editorial policy · Corrections
General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.