Skip to content
CalculatorBuddy

Day of the Week Calculator

Find the weekday for any date, its position in the year, remaining days and matching weekdays, and a calendar of that month.

ExampleSample values — edit any field to see your result.

Results update as you type.

Day of the Week

Sunday

Estimated result

Date
September 13, 2026
Day Number in Year
256
Days Left in Year
109
Weekday Number
#37 of 52 Sundays
Matching Weekdays Left
15

Month Calendar

SunMonTueWedThuFriSat
12345
6789101112
13141516171819
20212223242526
27282930
Day of the WeekSunday

Choose any date to find its weekday, day number within the year, remaining days, and the number of matching weekdays already passed and still ahead. A complete Sunday-through-Saturday calendar for the selected month is included.

Formula

Weekdays repeat every seven days. The calculation uses a whole-day UTC index, then applies the Gregorian leap-year rules when counting annual progress.

Examples

September 13, 2026

This date is Sunday, day 256 of 365. There are 109 days left, and it is the 37th of 52 Sundays in the year, leaving 15 Sundays.

Frequently asked questions

How does the calculator find a weekday?
It converts the Gregorian calendar date to a whole-day index and uses the known weekday of a reference date to determine the weekday reliably without timezone drift.
What does day number mean?
January 1 is day 1. The number increases through 365 in a common year or 366 in a leap year.
Does it support leap years?
Yes. Years divisible by 400 are leap years, as are years divisible by 4 unless they are divisible by 100.
What calendar is used?
The calculator uses the proleptic Gregorian calendar for valid ISO dates.

Related calculators