Day of the Week Calculator
Find the day of the week for any date — the day you were born, a historical event, or a date years ahead. Also shows when your birthday next lands on each day of the week.
- Free, no sign-up
- Private — runs in your browser
- Instant results
Enter your details
How the weekday of a date is worked out
The Gregorian calendar repeats exactly every 400 years. That cycle contains 146,097 days, and 146,097 divides evenly by 7 — which means the calendar for the year 2026 is identical to the calendar for 1626, and will be identical again in 2426. Every weekday calculation is ultimately a consequence of that fact.
Because a common year is 365 days, and 365 divided by 7 leaves a remainder of 1, a fixed date moves forward one weekday each year. A leap year has 366 days, a remainder of 2, so a date after 29 February jumps forward two.
Why your birthday drifts through the week
The one-day-forward, two-days-after-a-leap-year pattern produces a repeating cycle. Your birthday will fall on the same weekday after 6 years, then 11, then 6, then 5 — a 28-year cycle in which every day of the week is visited exactly four times.
The exact sequence depends on where your birthday sits relative to 29 February and where you are in the leap cycle, which is why the calculator lists your actual upcoming years rather than quoting a rule.
Doomsday: working it out in your head
John Conway's Doomsday rule is the best-known mental method. It relies on the observation that several dates always fall on the same weekday within a given year — 4/4, 6/6, 8/8, 10/10 and 12/12 among them. That shared weekday is the year's "doomsday".
For 2026 the doomsday is Saturday. So 4 April, 6 June, 8 August, 10 October and 12 December 2026 are all Saturdays, and any other date can be counted forward or back from the nearest anchor. With practice the whole calculation takes a few seconds.
The calculator above uses direct date arithmetic rather than Doomsday, because a computer has no reason to take the shortcut — but the rule is worth knowing if you want to do it without a device.
Common uses
- Curiosity about your own birth. The single most common reason people look this up.
- Planning ahead. Whether a future birthday, anniversary or deadline lands on a weekend.
- Genealogy. Old records sometimes state a weekday alongside a date; a mismatch is a useful sign of a transcription error.
- Checking historical claims. An event described as happening on a particular weekday can be verified against its date.
Frequently asked questions
What day of the week was I born?
Enter your date of birth above. The tool returns the weekday instantly, along with the date's position in the year and when your birthday next falls on each day of the week.
Why does my birthday change day each year?
A common year is 365 days, which is 52 weeks plus one day, so a fixed date moves forward one weekday each year. It jumps two days when a 29 February falls in between.
How often does my birthday fall on the same weekday?
Over a 28-year cycle it lands on each day of the week exactly four times, at gaps of 6, 11, 6 and 5 years. The cycle breaks at century years that are not divisible by 400, such as 1900 and 2100.
Can I check dates far in the past?
Yes. Bear in mind that countries adopted the Gregorian calendar at different times — Britain and its colonies in 1752, for example — so for dates before then, historical records may use the Julian calendar and give a different weekday.
What is the Doomsday rule?
A mental shortcut devised by John Conway. Certain dates (4/4, 6/6, 8/8, 10/10, 12/12) always share a weekday within a year, and every other date can be counted from the nearest of them.