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- Every date has a weekday, and this calculator finds it for any date from the year 1000 to 9999.
- It also gives the day of the year, the days left in the year, the ISO week number, the quarter and whether the year is a leap year.
- A last line shows how far the date is from today, so you can see at a glance if it is in the past or the future.
- The Gregorian calendar is used throughout, extended backward for dates before 1582.
How to use the day of week calculator
Pick a date
Choose the day, month and year with the date picker, or type the date in.
Read the weekday
The big result names the day of the week and spells out the full date.
Check the numbers
See the day of the year, days left in the year, ISO week number, quarter and leap-year status.
Compare with today
The last line shows how many days away the date is, or that it is today.
How the day of the week is worked out
Calendars repeat every seven days, so the weekday of any date comes down to counting days from a date whose weekday is already known. Computers count the days since a fixed starting date and take the remainder after dividing by seven. A remainder of zero means the same weekday as the starting date, one means the next weekday, and so on.
Weekday and year rules
Weekday = days since a known date, remainder after dividing by 7
Day of the year = days in the earlier months + the day of the month
Leap year = divisible by 4, but a century year must also divide by 400
ISO week 1 = the Monday to Sunday week that holds the first Thursday of the year
A leap year has 366 days because February gets a 29th day.
ISO weeks are used in many offices, schools and shipping calendars. Because a week always runs Monday to Sunday and week 1 is the one with the first Thursday, the first days of January can belong to week 52 or 53 of the previous year, and the last days of December can belong to week 1 of the next.
Worked examples
Example 1: a historic date
What day of the week was July 4, 1776?
Independence Day that year fell on a Thursday.
Example 2: a leap day
Look up February 29, 2024.
Because 2024 is a leap year, the year has one extra day.
Example 3: an ISO week edge case
Look up January 1, 2021.
So the first day of 2021 still belongs to the last ISO week of 2020.
Example 4: a sample date in 2026
Look up October 24, 2026.
Try your own date in the calculator above.
Leap years
Leap year examples
Applying the divide-by-4 rule with the century exception.
Leap years come around every four years, except for most century years.
Where a day of week calculator helps
Planning events
Check that a wedding, party or trip date lands on the weekday you want.
Work and school
Find the ISO week number used in schedules, timesheets and shipping plans.
History and family trees
Discover the weekday someone was born or an event took place.
Deadlines and contracts
See whether a due date falls on a weekend before you commit to it.
Count the days between two dates with the date difference calculator, add or subtract time with the add days to date calculator, or count business days with the working days calculator. For ages, see the age calculator. Public holidays differ by country, so check an official calendar for them.
Day of week calculator FAQ
How do I find the day of the week for any date?
Enter the date in the calculator and it shows the weekday at once. By hand, count the days from a date whose weekday you know and take the remainder after dividing by seven.
What is the ISO week number?
It is the week number defined by ISO 8601. Weeks run Monday to Sunday, and week 1 is the week that contains the first Thursday of the year.
How do I know if a year is a leap year?
A year is a leap year if it divides by 4, except century years, which must divide by 400. So 2000 and 2024 are leap years, while 1900 and 2100 are not.
Why do some dates belong to a different ISO year?
ISO weeks must be whole Monday to Sunday weeks. The first days of January can fall in week 52 or 53 of the previous year, and the last days of December can fall in week 1 of the next year.
Does the calculator work for old dates?
Yes, from the year 1000. It uses Gregorian rules throughout. Countries switched from the Julian to the Gregorian calendar at different times, so local records of historic dates may differ.
What does day of the year mean?
It is the position of the date in the year, counting January 1 as day 1. December 31 is day 365 in a normal year and day 366 in a leap year.