Day of the Week Calculator
Pick a date and press Find Day. The calculator names the day of the week, says whether it is a weekday or a weekend day and counts the days between that date and today. It reads any date from the year 1 to 9999 on the Gregorian calendar.
How to use the Day of the Week Calculator
- Enter your numbers in the Day of the Week Calculator above.
- Press the Find Day button to see the result.
- To try other numbers, change any value and press the button again.
How the weekday is found
Weekday = (days since January 1, 1970 + 4) mod 7, where 0 = Sunday and 6 = Saturday
January 1, 1970 was a Thursday, day 4 when Sunday is 0. The calculator counts the whole days from that date to yours on the Gregorian calendar, adds 4 and keeps the remainder after dividing by 7, which is always 0 to 6. Earlier dates count as negative days and land on the right weekday too.
Worked example
May 26, 2026 is a Tuesday. January 1, 2000 was a Saturday, so the calculator marks it as a weekend day. July 20, 1969, the day of the Apollo 11 moon landing, was a Sunday.
Frequently asked questions
Does this work for any year?
It works for any date from the year 1 to 9999, read on the Gregorian calendar. Most of Europe switched to that calendar from 1582 onwards and other countries later. A date written on the older Julian calendar has to be converted to Gregorian first, or the weekday comes out wrong.
Which dates does it refuse?
Dates that do not exist, such as February 30, or February 29 in a year that is not a leap year. The calculator then shows no result.
How are the days from today counted?
In whole calendar days, from today's date on your device to the date you picked. Tomorrow shows "In 1 day" and yesterday shows "1 day ago".