Day of Week Calculator
The Day of Week Calculator determines which day of the week any date falls on. Enter any date past or future and instantly see the day of the week. This tool is useful for planning events, checking historical dates, verifying birth days, or any scenario where you need to know the weekday of a specific date. It handles dates from any year, including historical dates and far future dates.
Formula
Day of week calculation: Zeller's Congruence or JavaScript Date object Days: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday JavaScript: new Date(year, month-1, day).getDay() Returns: 0 (Sunday) to 6 (Saturday)
Example
Date: 2026-09-09 Day: Wednesday Date: 2000-01-01 Day: Saturday Date: 1776-07-04 (US Independence) Day: Thursday
How to Use
- Enter the date you want to check
- The calculator shows the day of the week
- Use for planning, historical research, or curiosity
- Optionally check multiple dates
- Copy the result for your records
Frequently Asked Questions
How is the day of the week calculated?
The calculator uses date algorithms like Zeller's Congruence or the JavaScript Date object, which account for leap years and calendar rules. The Gregorian calendar (used since 1582) is the basis for all calculations.
Can I check dates before the Gregorian calendar?
The calculator uses the Gregorian calendar proleptically (extending it backward before its introduction). For dates before 1582, results may not match historical calendars, which used the Julian system. Most modern uses do not require pre-1582 dates.
What was the day of the week on a specific historical date?
Enter any historical date and the calculator shows the day of the week. For example, July 4, 1776 (US Independence) was a Thursday. December 7, 1941 (Pearl Harbor) was a Sunday.
Can I find dates that fall on a specific weekday?
This calculator shows the weekday for a given date. To find all dates that fall on a specific weekday (e.g., all Fridays the 13th in 2026), you would need to check each date individually or use a calendar tool.
Is the calculation accurate for future dates?
Yes. The Gregorian calendar is predictable, so future dates can be calculated accurately for thousands of years ahead. The calculator handles any valid date in the foreseeable future.