Day of the Week Calculator

Find the weekday for any date, like the day you were born or a holiday next year.

Dates use your browser’s date picker.
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Weekday
Day of the year
ISO week
Leap year?
Zeller’s formula check
Date

Saved Calculations

Items you add are saved in this browser.

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How to Find the Day of the Week

This page uses the Gregorian calendar and your browser’s date arithmetic, and double-checks with Zeller’s congruence:

h = (q + ⌊13(m + 1)/5⌋ + K + ⌊K/4⌋ + ⌊J/4⌋ + 5J) mod 7

q is the day of the month, m the month (March = 3 … January = 13 and February = 14 of the previous year), K the year within the century and J the century. h = 0 is Saturday, 1 Sunday, 2 Monday, and so on.

Worked Example

Tips

ISO week numbers start on Monday, and week 1 is the week containing the year’s first Thursday. Dates before 1582 are shown in the proleptic Gregorian calendar, which differs from the Julian calendar used then.