Day of the Week Calculator for Any Date

Enter a date to see which weekday it fell on or will fall on, with its day-of-year number, ISO week, leap year status and zodiac sign.

Runs in your browserFree, no sign-upLast reviewed October 8, 2026

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Quick answers

What day of the week was I born?: Enter your date of birth above and read Day of the week. As examples, June 15, 1990 was a Friday, January 1, 2000 was a Saturday and July 20, 1969 was a Sunday.
How do you work out the day of the week for any date?: Use a formula such as Zeller's congruence, which turns the day, month and year into a number from 0 to 6, or count forward from a date whose weekday you know and take the remainder after dividing the days by 7. The calculator above returns the weekday for any date you enter.
What day of the week will my birthday be next year?: One weekday later than this year, or two weekdays later if a February 29 falls between the two birthdays. October 8 is a Thursday in 2026, a Friday in 2027 and a Sunday in 2028, because 2028 is a leap year.
What day of the week is Christmas in 2026?: December 25, 2026 is a Friday. Christmas Day then falls on a Saturday in 2027, a Monday in 2028, a Tuesday in 2029 and a Wednesday in 2030.
What day of the week was January 1, 2000?: Saturday. It was day 1 of 366, since 2000 was a leap year, and the calculator shows ISO week 52: that week belongs to 1999, because ISO week 1 is the week containing the year's first Thursday.
Is day of the year the same as the date?: No. Day of the year numbers the days from 1 on January 1 to 365 or 366 on December 31. October 8, 2026 is day 281 of 365, and December 25 is day 359 in a common year and day 360 in a leap year.

Why use Day of the Week Calculator

Type or pick any date and the calculator names its day of the week, whether that is a birth date, a historical event or a date years ahead. June 15, 1990, for example, was a Friday. Next to the weekday you get weekend or weekday status, the day of the year (166 of 365 for that date), the ISO week number, whether the year is a leap year, the zodiac sign, and how many days ago or from now the date is. A table underneath lists the weekday of the same date in the three years before and the three years after.

Day of the week for well-known dates

Each weekday below is the calculator's result for that date.

Date	Event	Day of the week
July 4, 1776	US Declaration of Independence adopted	Thursday
April 15, 1912	Titanic sank	Monday
May 8, 1945	Victory in Europe Day	Tuesday
November 22, 1963	President Kennedy assassinated	Friday
July 20, 1969	Apollo 11 Moon landing	Sunday
November 9, 1989	Berlin Wall opened	Thursday
December 31, 1999	Last day of the 1900s	Friday
January 1, 2000	First day of the 2000s	Saturday
September 11, 2001	September 11 attacks	Tuesday
February 29, 2028	Next leap day	Tuesday

What day January 1 and December 25 fall on, 2026 to 2032

Year	January 1	December 25	Leap year
2026	Thursday	Friday	No
2027	Friday	Saturday	No
2028	Saturday	Monday	Yes
2029	Monday	Tuesday	No
2030	Tuesday	Wednesday	No
2031	Wednesday	Thursday	No
2032	Thursday	Saturday	Yes

In a common year January 1 and December 31 share a weekday, so December 25 is one weekday after January 1. In a leap year it is two weekdays after.

Worked examples with the full result

A birth date

Date June 15, 1990

Friday. Weekday, day 166 of 365, ISO week 24, not a leap year, zodiac sign Gemini. Surrounding years: 1987 Monday, 1988 Wednesday, 1989 Thursday, 1990 Friday, 1991 Saturday, 1992 Monday, 1993 Tuesday.

The jump from Saturday to Monday in 1992 is the leap day of that year.

A date at the turn of the year

Date January 1, 2027

Friday. Weekday, day 1 of 365, ISO week 53, zodiac sign Capricorn.

ISO week 53 here is the last week of 2026. The first ISO week of 2027 starts on Monday, January 4.

A leap day

Date February 29, 2028

Tuesday. Weekday, day 60 of 366, ISO week 9, leap year, zodiac sign Pisces.

In the surrounding-years table, years without a February 29 show the weekday of March 1 instead.

A historical date

Date July 4, 1776

Thursday. Weekday, day 186 of 366, ISO week 27, leap year, zodiac sign Cancer.

Zeller's congruence: the day of the week formula

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

q is the day of the month. m is the month, with March as 3 up to December as 12, and January and February counted as months 13 and 14 of the previous year. K is the last two digits of the year and J is the first two. The result h means 0 Saturday, 1 Sunday, 2 Monday, 3 Tuesday, 4 Wednesday, 5 Thursday, 6 Friday. For June 15, 1990: q = 15, m = 6, K = 90, J = 19. The terms are 15 + 18 + 90 + 22 + 4 + 95 = 244, and 244 mod 7 = 6, which is Friday, the same answer the calculator gives. This version of the formula is for the Gregorian calendar.

Why the same date moves through the week

A common year has 365 days, which is 52 weeks and 1 day. That one extra day pushes every date forward by one weekday the following year. A leap year has 366 days, 52 weeks and 2 days, so any date after February 29 moves forward by two weekdays, and dates in January and February make the two-day jump the year after.

A year is a leap year if it divides by 4, except century years, which must divide by 400. So 2000 was a leap year, while 1900 was not and 2100 will not be. Between 1901 and 2099 the pattern of weekdays and dates repeats every 28 years: a person born on a Friday has a birthday on a Friday again at ages 28, 56 and 84.

Friday the 13th follows from the same arithmetic. Any month that starts on a Sunday has one. In 2026 that happens in February, March and November.

Dates before the Gregorian calendar was adopted

The calculator applies today's Gregorian calendar rules to every date, including dates from before that calendar was in use. For most of the world's recent history this gives the weekday people actually lived through, including July 4, 1776 in the American colonies.

Earlier dates need care. Spain, Portugal and most of Italy switched from the Julian calendar in October 1582. Britain and its colonies switched in September 1752, when Wednesday, September 2 was followed by Thursday, September 14. Russia changed in 1918. A date written down before the local switch was recorded in the Julian calendar, so its real weekday differs from the one shown here. For example, the calculator gives Saturday for September 2, 1752, but in Britain that day was a Wednesday.

The zodiac sign shown is the Western sun sign using fixed date ranges, for example Aries from March 21 to April 19. The actual moment the sun changes sign varies slightly from year to year, so a birth date on the first or last day of a range may belong to the neighboring sign.

Step by step

1
Enter the Date by typing it or choosing it in the date picker. Use your date of birth to find the day you were born.
2
Read Day of the week and Weekend or weekday at the top of the results.
3
Check Day of the year, ISO week number, Leap year and Zodiac sign for the extra details about that date.
4
Look at the table called That date over the surrounding years to see which weekday the same date falls on from three years earlier to three years later.

Questions people ask

Can I look up a date in the future?

Yes. Any valid date works, past or future. December 25, 2030, for instance, is a Wednesday. For future dates the last figure in the results reads Days from now, and for past dates it reads Days ago.

What is the ISO week number shown in the results?

It is the ISO 8601 week, where weeks run Monday to Sunday and week 1 is the week containing the first Thursday of the year. The first days of January can therefore fall in week 52 or 53 of the previous year, and the last days of December can fall in week 1 of the next.

Does the result depend on my time zone?

The weekday, day of the year, week number and zodiac sign depend only on the calendar date you enter. The Days ago or Days from now figure compares that date with today's date on your device, so it can differ by one for people on opposite sides of midnight.

Which days count as the weekend?

Saturday and Sunday are labeled Weekend and Monday to Friday are labeled Weekday. This cannot be changed in the tool, so adjust for yourself if your working week runs differently.

How does the surrounding-years table handle February 29?

For a leap-day date, years that have no February 29 show the weekday of March 1. The leap years in the table show the true weekday of February 29.

How often does my birthday fall on the same day of the week?

The gaps are usually 5, 6 or 11 years, in a pattern that depends on where your birth date sits in the four-year leap cycle. Across any 28-year span between 1901 and 2099 each date other than February 29 lands on each weekday exactly four times.

Does the week start on Sunday or Monday here?

The ISO week number assumes weeks that start on Monday. Calendars in the United States usually start the week on Sunday and number weeks from January 1, so a US-style week number can differ from the ISO week shown. The weekday name itself is the same under either convention.

What was the day of the week when the Gregorian calendar began?

Friday. The first day of the Gregorian calendar was October 15, 1582, which followed directly after Thursday, October 4, 1582 in the Julian calendar. The calculator returns Friday for October 15, 1582.