What Day Was I Born? Day of the Week Calculator

Enter any date to see which day of the week it falls on, along with its day of the year and ISO week number.

Last updated: 8 November 2026

What the result shows

Besides the weekday, the result gives the day of the year (1 January is day 1) and the ISO week number. Dates are calculated with the Gregorian calendar, which most countries adopted between 1582 and the early 20th century — so for older dates, the weekday is the "proleptic" Gregorian one and may differ from what was written at the time in Julian-calendar countries.

1 January and Christmas Day by year

Working it out by hand

A common year is 52 weeks plus 1 day, so a date moves forward one weekday each year — two after 29 February in a leap year. Christmas 2026 is a Friday, so Christmas 2027 is a Saturday and Christmas 2028, after a leap day, is a Monday. Mathematician John Conway's Doomsday rule builds on this: in every year, 4/4, 6/6, 8/8, 10/10, 12/12, the last day of February, and 9/5, 5/9, 7/11 and 11/7 all fall on the same weekday. In 2027 that "doomsday" is a Sunday, so 4 April, 6 June and 12 December 2027 are all Sundays.

Monday's child

The English nursery rhyme gives each birth weekday a trait: "Monday's child is fair of face, Tuesday's child is full of grace, Wednesday's child is full of woe…". In Ghana's Akan tradition, children receive a day name — Kofi or Afua for Friday, Kwame or Ama for Saturday — and in Thailand each weekday has its own colour, with Monday's yellow linked to the late King Bhumibol.

Frequently asked questions

What day of the week was I born?

Enter your birth date above to see the weekday.

What day is Christmas 2027?

Saturday 25 December 2027.

What day was 1 January 2000?

A Saturday.

Does it work for old dates?

Yes, using the Gregorian calendar extended backwards.