About the Day of the Week Calculator
Pick a date and this calculator tells you which day of the week it is, whether it is in the past or the future. It is useful for finding the day you were born, checking what weekday a historical event fell on, or planning a date far ahead. Alongside the weekday it shows the day of the year, the ISO week number, whether the year is a leap year and how many days the date is from today. It uses the Gregorian calendar, extended backwards for dates before it was adopted.
Updated October 2026
How to use the Day of the Week Calculator
- 1Choose a date with the date picker, or type it as year-month-day.
- 2Read the weekday in the large answer box.
- 3Check how many days the date is from today.
- 4Look at the day of the year, ISO week and leap-year rows for extra facts.
- 5Press Copy result to share the answer.
Why people look up weekdays
Common reasons include finding the weekday of a birthday or anniversary, checking a historical date for a school project, confirming that a booking or deadline falls on a working day and planning events a year or more ahead. Knowing whether a future date falls on a weekend saves time when scheduling venues, travel and meetings.
What the extra rows tell you
- Day of the year: handy for logs, agricultural calendars and some date codes
- ISO week: used in business planning, shipping and many European schedules
- Leap year: tells you whether February has 29 days
- Position in month: for rules like the second Tuesday or the last Friday
Tips and limits
Enter dates as year, month, day if you type them. The picker shows the format your device prefers but the result is the same. Dates with a day that does not exist, such as 31 April or 29 February in a non-leap year, are rejected rather than silently corrected. For counting between two dates, use the Days Between Dates tool.
Related tools
The Date Calculator adds or subtracts days, months and years, the Week Number Calculator focuses on week numbering, and the Age Calculator turns a birth date into years, months and days. The Working Days Calculator skips weekends for deadlines.
Features
- Weekday for any valid date from year 1
- Distance in days from today
- Day of the year (1 to 365 or 366)
- ISO 8601 week number and week-year
- Leap year check
- Position in the month, such as the 3rd Friday
- Rejects impossible dates like 30 February
- Runs in your browser
Frequently asked questions
How do I find out what day I was born on?
Pick your birth date in the date box and the weekday appears straight away. It also shows how many days ago that was, so you can see roughly how many days you have been alive.
How is the day of the week worked out?
The calculator counts the days between your date and a known reference date, 1 January 1970 which was a Thursday, and takes the remainder when divided by seven. Calendar rules for leap years are built in, so the result is exact for the Gregorian calendar.
What is the ISO week number?
ISO 8601 weeks start on Monday, and week 1 is the week that contains the first Thursday of the year. This means that early January can belong to week 52 or 53 of the previous year, and late December can belong to week 1 of the next. The calculator shows both the week and its year.
Is 2024 a leap year, and how are leap years decided?
Yes, 2024 is a leap year. A year is a leap year if it is divisible by 4, except for century years, which must also be divisible by 400. So 2000 was a leap year, but 1900 and 2100 are not. The tool shows this for every date you pick.
Can I check dates before 1582?
You can, but the result uses the Gregorian calendar projected backwards. Different countries switched from the Julian calendar at different times, from 1582 to the early 1900s, so a historical record may name a different weekday for an old date in the local calendar of the time.
Does it use my time zone for today's date?
Yes. The distance from today uses today's date on your device, so it matches your calendar. The weekday of the date you pick does not depend on any time zone.