Day-of-Week Calculator

Find what day of the week any date falls on.

Need the ISO week number too? See Week Number Calculator.

Worked example

January 1, 2027 falls on a Friday. Calendar systems compute this by counting the total number of days since a known reference date and taking the remainder after dividing by 7, using the proleptic Gregorian calendar for any date, including ones before its historical adoption.

Limitations

This uses the proleptic Gregorian calendar throughout; it does not reflect the historical calendar actually in use in a given region on a very old date.

Frequently asked questions

Does this work for dates far in the past or future?: Yes, using the proleptic Gregorian calendar extended in both directions.