Day of Week Calculator
Enter any date to find what day of the week it was or will be.
Try it with this example
Enter 1990-01-15 to see it was a Monday. Works for any date in the past or future.
What is this tool?
The Day of Week tool answers a simple but often hard-to-remember question: what weekday was (or will be) a given date? Enter January 15, 1990, and you learn it was a Monday. Enter a future date—your wedding, a conference—and you see which day it falls on. The tool uses standard Gregorian calendar rules and handles leap years, so results are accurate for dates within its supported range.
Historical dates work too. Check what day the Declaration of Independence was signed, or when a famous event occurred. Some people care about "Friday the 13th" or "Monday blues"; others need it for scheduling, travel, or record-keeping. The calculation is deterministic: given a date, the weekday is fixed. No guesswork, no manual calendar flipping.
Implementation follows well-known algorithms (e.g. Zeller's congruence or similar) that account for the Gregorian calendar's rules. The tool runs entirely in your browser. No server, no API, no data sent. Enter any valid date and get the result instantly.
Use it when planning events, writing historical content, filling out forms that ask for "day of week," or satisfying curiosity about past or future dates. Teachers can use it for calendar lessons; researchers for chronology. It's a small utility that removes the need to open a calendar app or write a quick script.
Bookmark it for the next time someone asks "What day was that?"—you'll have the answer in seconds.