Was your birthday on a weekend this year, and what day will your anniversary fall on in 2030? Pick a date and this tool tells you the weekday, whether the year is a leap year, and the weekday of the same date over the following years.
How to use it
- Choose a date.
- Read the weekday.
- Look down the list of later years.
- Copy the answer.
When it helps
- Finding out what day you were born.
- Planning an event on a future date.
- Checking historical dates.
- Seeing when a birthday falls on a weekend.
Good to know
- Dates use the Gregorian calendar throughout, even for years before it was adopted.
- A 29 February skips years that aren't leap years.
- Only the date is used, so time zones don't matter.
How the weekday is found
The tool counts the days between your date and a known reference date and takes the remainder when divided by seven. That's the same idea behind classic mental methods such as Zeller's congruence and the doomsday rule invented by mathematician John Conway.
It uses the Gregorian calendar throughout, which most of the world adopted from 1582, with different countries switching at different times. For very old dates, history may differ.
Worked example: a birthday
If you were born on 15 January 2000, the tool shows Saturday. The table of later years shows that in 2026 it falls on a Thursday, and in 2028 it falls on a Saturday again, since 2028 is a leap year, which shifts weekdays by two instead of one.
For birthdays, anniversaries and holidays, that list lets you plan ahead, such as when a date will land on a weekend.
Weekday patterns
A normal year has 365 days, which is 52 weeks plus one day, so dates move forward one weekday each year. In a leap year they move two. That's why a calendar repeats only every 28 years, with exceptions around century years.
Friday the 13th happens at least once and at most three times in any year, and the 13th falls on a Friday slightly more often than any other weekday.
Fun weekday facts
The same calendar repeats whenever a year starts on the same weekday and has the same leap-year status. For 2026, which starts on a Thursday, the calendar matches 2015 and will match 2037. Since the 400-year Gregorian cycle contains an exact number of weeks, the whole pattern repeats every 400 years.
Weekday names come from the seven classical planets in many languages, from Sun-day through to Saturn-day.
A quick mental method
You can find weekdays in your head with the doomsday rule: certain dates in each year, like 4 April, 6 June, 8 August, 10 October and 12 December, always share a weekday. Learn that day for the year and count from the nearest anchor date.
Questions
What day was 1 January 2000?
A Saturday.
Does it work for very old dates?
Yes, though history used different calendars.