Understanding the result
The large result is the weekday. The details beneath describe where the date sits in its year: the day number (1 is 1 January), the ISO 8601 week and week-year, the calendar quarter, whether the year is a leap year and how many days remain in the year.
What is a day of the week calculator?
It tells you the weekday of any past, present or future date: what day you were born, what day a historical event happened or which day a future deadline falls on.
How it works
The date is converted to a day count from 1 January 1970, which was a Thursday. Taking that count modulo 7 gives the weekday exactly, with no lookup tables and no dependence on your time zone.
The Gregorian calendar is applied to all years. Dates before the calendar was adopted in a given country (from 1582 onward) were recorded on the Julian calendar, so a historical date can fall on a different weekday in the sources of the time than it does here.
Examples
1 January 2000
Saturday. It is day 1 of a leap year, in ISO week 52 of 1999, in Q1.
29 February 2024
Thursday, day 60 of 366 in a leap year, in ISO week 9.
4 July 1776
Thursday on the Gregorian calendar, which is the calendar the date is normally quoted in.
Things to keep in mind
- Weekday names are given in English. The ISO week starts on Monday, whereas many countries start the week on Sunday for calendars.
- For historical dates before the Gregorian calendar was adopted where you live, contemporaneous records may use the Julian calendar.
- The tool supports dates from the year 1 to the year 9999.