What day of the week was it?
Pick any date, past or future, and find out which day of the week it falls on.
Find the weekday for any date
Enter a date to find whether it falls on a Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday. It works for past and future dates, so you can check birthdays, anniversaries, historical dates, appointments, and planned events.
For related date planning, you can also calculate the number of days between two dates or add a specific number of days to a starting date.
How weekday calculation actually works
Every date in the modern Gregorian calendar maps to exactly one weekday, following a repeating pattern based on how many days have elapsed since a fixed reference point. Because a standard year (365 days) isn't evenly divisible by 7, a given calendar date shifts to a different weekday most years — which is exactly why "my birthday was a Tuesday last year" often isn't true the following year. Leap years complicate the pattern slightly further, since they insert an extra day that shifts everything after February 29th by one additional weekday compared to a non-leap year.
Why people look up historical weekdays
Beyond planning future events, this calculator gets used to answer genuinely interesting historical questions — what day of the week a birth date, a historical event, or a grandparent's wedding date fell on. Genealogy researchers use weekday lookups to cross-check historical records, since old documents sometimes record a date but not the day of the week, or vice versa, and a mismatch can be a clue that a record contains an error.
Related tools: Days between two dates · Add or subtract days
Frequently asked questions
Does this work for dates far in the past?
Yes — it works for any valid calendar date, using the standard Gregorian calendar (adopted at different times in different countries, generally from 1582 onward).
Why did my birthday fall on a different weekday last year?
Because 365 isn't evenly divisible by 7, most calendar dates shift forward by one weekday each year (or two, across a leap year), which is why a fixed date rarely lands on the same weekday two years running.
Weekday of a future or past date
Weekdays follow a seven-day cycle, shifted by leap days. Asking “what day is 15 August 2031” is a calendar question, not a holiday question. The result does not tell you whether that date is a public holiday in your country.
People use this page to plan weddings, product launches, and school terms. After you have the weekday, check local holiday lists separately if shops or offices must be open.