Day of the Week Finder

Which weekday were you born on? What about the date on a family document or a contract deadline in 2031? Type the date with a four digit year and two digit month and day, like 1889-11-15, and the answer updates as you type. Brazilian independence, 7 September 1822, fell on a Saturday. The abolition law of 13 May 1888 landed on a Sunday. The Apollo 11 landing, 20 July 1969, was also a Sunday.

The trap sits in old dates. The calculation uses the proleptic Gregorian calendar, applying today's rules backwards even to centuries when they did not exist. Portugal and its colonies only adopted the Gregorian calendar in October 1582, and before that records were kept in the Julian calendar. Typing 1500-04-22, the date Cabral sighted Brazil, returns Sunday, yet that Julian 22 April was a Wednesday. In Gregorian terms it corresponds to 2 May 1500.

Write the full year, padding with zeros if needed, and two digits for month and day: 1822-09-07. Formats like 7/9/1822 return a dash. Two things to watch: years below 100 are read as twentieth century dates, so 0044-03-15 answers as if it were 1944, and impossible dates roll over silently, with 2026-02-30 answering as 2 March. From the twentieth century onward the result is dependable. Everything runs in your browser.