Day of the Week Calculator

This calculator uses your browser's Gregorian calendar to find the weekday, and the week number counts weeks starting on Sunday (not the ISO week number). Facts: a common (non-leap) year starts and ends on the same weekday, while a leap year ends one weekday later than it started. The Gregorian calendar repeats every 400 years because 400 years have 146,097 days, which is exactly 20,871 weeks.