How to use this tool
Enter a valid date and calculate. The answer uses the proleptic Gregorian calendar: Gregorian rules are extended backward even before a country adopted that calendar. For historical records originally written using the Julian calendar, first convert the date to Gregorian. The result also includes the ordinal day of the year, starting with January 1 as day 1.
Try these values
October 19, 2026 falls on a Monday. January 1, 2000 was a Saturday. February 29, 2028 falls on a Tuesday, and is day 60 of that leap year.
Useful for birthdays and planning
You can check the weekday for an upcoming birthday, the first day of a course or a date in an old record. The day-of-year result counts January 1 as day one. It can help when comparing dated logs, but it is a different number from an ISO week number. Use the week number calculator if your planner labels weeks rather than individual days.
Be careful with very old records
The Gregorian calendar was adopted at different times in different places. A date copied from an older local or Julian calendar is not necessarily the same Gregorian date written with the same numbers. This tool consistently uses Gregorian rules, including for earlier years. Check which calendar the original record used before trying to resolve a historical disagreement about the weekday.
Common questions
Can I use historical dates?
Yes, within the supported range of years 1–9999. The interpretation is always Gregorian, which may differ from a historical local calendar.
How are leap years identified?
Years divisible by four are leap years, except centuries not divisible by 400.
Is Sunday day zero?
The tool prints the weekday by name, so there is no numbering ambiguity.
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