Date Difference Calculator
Find the exact time between two dates in years, months and days, or the date that falls a set number of days, weeks, months or years before or after another.
Time between two dates
Add to or subtract from a date
Worked out on your device from calendar dates only, so time zones and daylight saving don’t change the count. Nothing is sent or saved.
Count the time between two dates
How many days until a wedding, how long a lease ran, how old a house is: questions like these come down to the span between two dates. Counting it on a calendar is slow and easy to get wrong, with months of different lengths and leap years in the way. This calculator counts it exactly, and also works the other way: start from a date and add or subtract time to find a new one.
How to use it
- Under Time between two dates, pick a start date and an end date. Today is filled in as the start.
- Tick Include the end date if the last day should count, as for a trip or a course.
- Read the span in years, months and days, then as total days, as weeks and days, and as hours.
- To find a date instead, pick one under Add to or subtract from a date, choose Add or Subtract, and fill in the years, months, weeks or days.
How the counting works
- Whole months first: the tool counts the most whole months that fit, then the days left over. March 15 to May 20 is 2 months and 5 days.
- Short months: when a month doesn’t have the day you start from, its last day stands in. January 31 plus one month is February 28, or February 29 in a leap year, and the tool says so when it happens.
- Adding a mix: years and months are added together first, then weeks and days. February 29, 2024 plus 1 year and 1 month is March 29, 2025.
- Swapped dates: if the end date comes first, the tool counts from the earlier date and tells you.
Worked examples
- A year: January 1 to December 31, 2026 is 364 days, or 365 with the end date included.
- A leap year: January 1, 2024 to January 1, 2025 is 366 days.
- Before 1970: July 20, 1969 to January 1, 1970 is 5 months and 12 days, or 165 days.
- Thirty days on: 30 days after October 20, 2026 is Thursday, November 19, 2026.
Good to know
- Calendar: dates run from year 1 to 9999 on the Gregorian calendar used today, carried back before it began in 1582, so very old dates may differ from historical records.
- Private: everything is worked out on your device; nothing is sent or saved.
- Related: the Age Calculator adds the next birthday, and the Working Days Calculator leaves out weekends and holidays.
Frequently asked questions
What does “Include the end date” do?
It counts the last day too. Monday to Friday is 4 days without it and 5 days with it, the way you’d count the days of a trip or a course that runs through the Friday. Leave it off to measure the gap between two dates, as in “how long until”.
How are months counted when they have different lengths?
A month runs from a date to the same date in the next month, so the tool counts whole months first, then the days left over. When the next month is too short, its last day stands in: January 31 to February 28 is one month in a year that isn’t a leap year.
Does it work for dates before 1970 and in leap years?
Yes. It counts whole days on the Gregorian calendar from year 1 to 9999, with February 29 in every leap year: years divisible by 4, except century years not divisible by 400. So 2000 was a leap year and 1900 wasn’t.
Why might the hours differ from a real clock?
The tool counts every day as 24 hours. Where clocks change for daylight saving time, the day they go forward has 23 hours and the day they go back has 25, so a span that crosses a change is an hour shorter or longer on a wall clock.