How can the day of the week be calculated for any date?

Calendar algorithms such as Zeller's congruence and Conway's Doomsday rule convert a date's year, month, and day into a weekday index mathematically. This calculator applies the same logic the Gregorian calendar follows, so no lookup tables are needed.

What is the Doomsday rule?

A mental-math method by John Conway: certain easy dates ("doomsdays" like 4/4, 6/6, 8/8, 10/10, 12/12) always share the same weekday within a year. Find that year's doomsday from an anchor value, then count from the nearest doomsday to your target date.

Why does the same date fall one weekday later each year?

A common year has 365 days, which is 52 weeks plus 1 day, so every date advances one weekday from one year to the next. After a leap day intervenes, dates jump two weekdays — which is why the pattern repeats only every 28 years (barring century rules).

Does this work for very old historical dates?

Weekday math assumes the Gregorian calendar, adopted in 1582 by Catholic countries but much later elsewhere (Britain and its colonies in 1752, Russia in 1918). For dates before a region's switch, the historical (Julian) weekday differs from the back-calculated Gregorian one.

Day Of Week Calculator

Find what day of the week any date falls on. Free, fast, accurate — no signup, mobile-friendly, works in any browser.

Date Selection

What would you like to find?

Select Date

Options

Show next occurrences of this day

Include holidays and special dates

Did You Know?

• The Gregorian calendar has a 400-year cycle
• January 1, 2000 was a Saturday
• Friday the 13th occurs at least once every year
• Some years have 53 weeks instead of 52
• The concept of weekdays dates back to ancient civilizations

Day of Week

Tuesday

Tuesday, July 28, 2026

Week Number

Week of year

Day of Year

209

Day 209 of 365

Date Information

Weekend:No

Season:Summer

Zodiac Sign:Leo

Moon Phase:Full Moon

Next Occurrences

Next Tuesday (1 week later):8/4/2026

Next Tuesday (2 weeks later):8/11/2026

Next Tuesday (3 weeks later):8/18/2026

Next Tuesday (4 weeks later):8/25/2026

How it works

This calculator tells you which day of the week any date falls on — past or future. It works from a known reference date and the fixed 7-day cycle, adjusting for leap years, so you can find the weekday of a birthday, holiday, or historical event.

Weekday from a date

Weekday = (reference weekday + days elapsed) mod 7

days elapsed: days from a known reference date
mod 7: the repeating 7-day cycle

Worked example

What day was July 4, 1776?

Count the cycle from a known reference

It was a Thursday.

Good to know

The Gregorian calendar repeats its day-date pattern every 400 years.
Leap years shift later dates by an extra day, which the calculation accounts for.
Algorithms like Zeller's congruence compute the weekday directly from the date.