What Day of the Week Was It?
Ever wondered what day of the week was January 1, 2000 — or your birthday, your wedding day, or any date at all? Enter a date and this free day of the week finder tells you the weekday instantly, plus how long ago it was (or how far in the future it is). It works for any year from 1 to 9999, with all math done in UTC so your time zone can never shift the answer.
Enter a date
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Your results
| Detail | Value |
|---|---|
| Full date | — |
| Time from today | — |
| Total days away | — |
| Day of the year | — |
| ISO week number | — |
| Leap year | — |
How to use this calculator
Pick a month, type the day and year, and the weekday appears instantly — no button press needed. Use the quick-try links (Jan 1, 2000, the Moon landing, or Independence Day 1776) to jump to a famous date. Anything from year 1 to year 9999 works, past or future.
Besides the weekday, you get the full calendar date, how long ago the date was (or how far ahead) in years, months, and days, the total day count, the day of the year (e.g. Jan 1 is day 1 of 365), the ISO week number, and whether the year is a leap year.
How it works
The weekday comes from JavaScript's Date.UTC(y, m-1, d).getUTCDay(), which returns 0 for Sunday through 6 for Saturday — the same seven-day cycle the calendar has kept without a break for millennia. Doing it in UTC (not local time) means daylight saving and time-zone offsets can never push the date into a neighboring day and flip the answer.
The one assumption to know about: the math uses the proleptic Gregorian calendar, extending today's leap-year rules (divisible by 4, except centuries unless divisible by 400) backward before 1582. Real countries adopted the Gregorian calendar on different dates, so for pre-switch dates the answer is the calendar-math result, not the historically observed weekday. Years 1–99 are handled explicitly with setUTCFullYear so the old JavaScript quirk that remaps them onto 1900–1999 can't affect the result. All counting is exact — nothing here is an estimate.
Frequently asked questions
How do I find out what day of the week a date was?
Enter the month, day, and year and this calculator tells you the weekday instantly. For example, January 1, 2000 was a Saturday, and July 20, 1969 (the Moon landing) was a Sunday.
Is this calculator accurate for dates before 1900?
The math is exact under one assumption: it uses the proleptic Gregorian calendar, meaning today's Gregorian leap-year rules are extended backward through all history. Real countries switched from the Julian calendar to the Gregorian at different times (Britain and its colonies in 1752, for example), so a weekday from before the local switch is the calendar-math answer, not the historically observed one.
Why do some weekday tools give me the wrong day?
The usual bug is a time-zone shift. Code like new Date("2000-01-01") parses as UTC midnight, and your time zone then moves it into the previous or next day, flipping the weekday. This page computes everything at UTC midnight, so the weekday is the same no matter where in the world you are.
What is the proleptic Gregorian calendar?
It is the Gregorian calendar extended backward before its 1582 introduction, as if the leap-year rules (a year is a leap year when divisible by 4, except centuries unless divisible by 400) had always applied. It is the standard convention astronomers and programmers use for old dates.
Can I check future dates too?
Yes. Enter any date from year 1 to year 9999 — past, present, or future — and you'll get the weekday, plus how far away the date is from today in years, months, and days.