Day of the Week Calculator

Find which day of the week any date falls on, plus the day of the year and ISO week number. Enter the year, month, and day.

Day of the Week
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For this date.

Usage Tip

Useful for scheduling: check which weekday a future date lands on before planning around it.

THE MATH
The weekday is computed from the calendar date.
Day of year and ISO week number follow from it.
Every date falls on a fixed weekday determined by the calendar.
ISO week numbering starts weeks on Monday and assigns week 1 to the week containing the first Thursday of the year.
Enter month as 1 to 12 and a valid day for that month.
ISO week can be 52 or 53 depending on the year.
Leap years (shown here) have 366 days, adding Feb 29.
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