Day of the week calculator for any date

How to use the day of the week calculator

1. Choose the month, then type the day and the year. The year must be in full, such as 1990, not 90. The calculator opens on today's date.
2. Read the weekday at the top of the result, with a sentence such as "May 15, 1990 was a Tuesday".

Under it you get the day of the year (January 1 is day 1), the ISO week number (more on the week number page), which one of that weekday it is in the month, such as the 3rd Tuesday of May, how far the date is from today, and the number Excel's WEEKDAY function would give. The steps under the form work the answer out by hand with Zeller's congruence for your date. It works for any date from the year 1 to 9999; for dates before the 1750s, see the section on old dates.

What day of the week was I born?

Enter your date of birth: someone born on May 15, 1990 was born on a Tuesday. The result also shows the weekday of your birthday this year and next.

A birthday moves on by one weekday each year, because a common year of 365 days is 52 weeks and 1 day. When a February 29 comes between one birthday and the next, it moves by two days instead:

For someone born on February 29, the calculator shows February 28 in years without a leap day. For your exact age in years, months and days, use the age calculator.

The day of the week formula (Zeller's congruence)

Zeller's congruence turns a date into a number from 0 to 6. It needs four numbers:

• q, the day of the month;
• m, the month, with March as 3 up to December as 12. January and February count as months 13 and 14 of the year before, so January 1, 2000 is worked out as month 13 of 1999;
• K, the last two digits of the year, and J, the digits before them (19 for 1990).

Then add q, 13 x (m + 1) / 5 rounded down, K, K / 4 rounded down, J / 4 rounded down and 5 x J. Divide the total by 7 and keep the remainder: 0 is Saturday, 1 Sunday, 2 Monday, 3 Tuesday, 4 Wednesday, 5 Thursday and 6 Friday. Here it is for July 4, 1776:

A remainder of 5 means Thursday. The K / 4 and J / 4 parts count the leap days, and 5 x J allows for how far each whole century moves the weekdays on, including the century years that are not leap years. The calculator above shows these steps for whatever date you enter.

Old dates: the Gregorian and Julian calendars

The calendar we use today, the Gregorian calendar, did not exist before 1582. The US Naval Observatory explains that under the scheme of Pope Gregory XIII, "for dates on or after 15 October 1582, the Gregorian calendar is used", and that the older Julian calendar "has a leap year every fourth year", with no exception for century years. The change skipped 10 dates, but the observatory notes there was "no discontinuity in Julian dates or days of the week": Thursday, October 4, 1582 was followed by Friday, October 15.

Not every country changed at once. The observatory says that "for England and its colonies, the change did not occur until September 1752". The Calendar (New Style) Act 1750 made the day after September 2, 1752 "the fourteenth day of September", "omitting for that time only the eleven intermediate nominal days". In the calculator, Julian September 2, 1752 is a Wednesday and Gregorian September 14, 1752 is a Thursday, the very next day.

This calculator uses the Gregorian calendar for every date, counted back before 1582 where needed (the proleptic Gregorian calendar). For a date before October 15, 1582, or before September 14, 1752 in Britain and its colonies, the result also gives the Julian date people wrote at the time. For a date taken from an old record, open Calendar for old dates and choose Julian.

One more trap: before 1752 the English year number changed on March 25, not January 1. The Act describes the old reckoning "according to which the year beginneth on the twenty-fifth day of March". A record dated in January to March 24 may therefore show the earlier year, or both years, such as 1750/51. Enter the later year.

Excel day of week: TEXT and WEEKDAY

With a date in cell A2, these formulas work in both Excel and Google Sheets:

Microsoft's example =TEXT(TODAY(),"DDDD") gives "Today's day of the week, like Monday". WEEKDAY "Returns the day of the week corresponding to a date", and by default "The day is given as an integer, ranging from 1 (Sunday) to 7 (Saturday)". In Google Sheets, WEEKDAY "returns the day of week in numeric form", and Google says "To get the name of the weekday, use the TEXT function or change the number formatting on the cell".

Excel cannot work with dates before 1900. Microsoft says Excel for Windows uses the 1900 date system, "which means the first date is January 1, 1900", and a year typed into DATE from 0 to 1899 is added to 1900, so =DATE(1776,7,4) gives a date in 3676. Use the calculator above for older dates.

Questions and answers

Sources

Checked on 9 October 2026. If a rule has changed, please tell us.

• US Naval Observatory: Julian Date Converter (Gregorian and Julian calendars)
• legislation.gov.uk: Calendar (New Style) Act 1750, section 1
• legislation.gov.uk: Calendar (New Style) Act 1750, introduction
• Microsoft Support: WEEKDAY function
• Microsoft Support: TEXT function
• Microsoft Support: DATE function
• Google Docs Editors Help: WEEKDAY function
• Google Docs Editors Help: TEXT function