Age Calculator Between Two Dates
Work out the exact time between any two dates — in full years, months and days, with the total days, weeks and months too.
Exact difference:
Total days:
Total weeks:
Total months:
The calculation happens in your browser — your dates are not sent anywhere.
How to use the age calculator between two dates
Pick a start date and an end date, and the calculator works out the exact time between them straight away. You can use it for a birthday, an anniversary, a work anniversary, a project, a loan term, or any two dates you are curious about. There is nothing to install, and there is no sign-up. The result updates the moment you change either date, so you can try different dates as quickly as you can pick them. Everything is worked out in your browser, so the dates you enter never leave your device.
- Choose a start date — the earlier date, such as a date of birth, the day a job started, or the day a project began.
- Choose an end date — the later date, such as today, a birthday, or a date in the future. The end date is already filled in with today's date, so you only need to change it if you want a different end point.
- Read the result — the exact difference in full years, full months and remaining days, plus the total days, total weeks and total months between the two dates.
Worked example: 1 January 2000 to 1 January 2026
Take 1 January 2000 as the start date and 1 January 2026 as the end date. The calculator gives an exact difference of 26 years, 0 months and 0 days, because the two dates fall on the same day and month, 26 years apart. The total days between them is 9,497. That is not 26 times 365, which would be 9,490: seven leap days fall inside the span — 29 February 2000, 2004, 2008, 2012, 2016, 2020 and 2024 — and each one adds a day. The total weeks are 1,356.7, and the total months are 312. Try the same two dates in the calculator above and you will see the same four numbers.
How the exact difference is worked out
The exact difference counts full calendar years first, then full calendar months, then the days that are left over. Starting from the start date, the calculator counts whole years until adding another year would pass the end date, then whole months until adding another month would pass it, then the remaining days. This is why the answer is always given in calendar units, and why the months and days in the result are always smaller than a full year and a full month.
When the end day of the month is earlier than the start day, the calculator borrows days from the month before the end date. For example, from 15 June 1990 to 6 November 2026 the years come to 36, the months come to 4, and the days come to 22, because October has 31 days: counting back from 6 November to 15 October is 22 days. Borrowing is what keeps the result exact instead of rounding the months.
Leap years are handled by the real calendar, never by dividing by 365. The calculator works with real dates, so every 29 February between the two dates counts as a day. The total days figure is a plain count of the days between the two dates, while the total weeks are the total days divided by 7, shown to one decimal place, and the total months are the full years times 12 plus the full months. All four figures describe the same span of time — they are just different ways of measuring it.
When the total figures are useful
The exact difference is the figure most people want: how old someone is, or how long it has been since a date. The total days are handy when a form or a contract asks for a number of days, for example the length of a notice period or the gap between two events. The total months work the same way for things measured in months, such as a loan term or a tenancy. Total weeks are useful for tracking a project week by week. Because all four figures come from the same two dates, they can be mixed and matched without ever disagreeing.
Frequently asked questions
How is the age between two dates calculated?
The calculator counts the full calendar years between the two dates first, then the full months left over, then the remaining days. For example, 1 January 2000 to 1 January 2026 is exactly 26 years, 0 months and 0 days. The total days, total weeks and total months are separate counts of the same span, so they always agree with the exact difference.
Does it count leap years?
Yes. The calculation uses real calendar dates, so every 29 February that falls between the two dates is counted as an extra day. That is why the total days from 1 January 2000 to 1 January 2026 is 9,497, not 9,490: the seven leap days in the span are all included.
What if I only know the year?
Use 1 January of that year as an estimate. The result will be exact for the dates you enter, but remember that it is only as accurate as the dates you know: if the real date was later in the year, the true age will be a little smaller than the figure shown.
Can I use future dates?
Yes. You can enter any two dates, in the past or in the future. The start date should be the earlier date and the end date the later one; if you enter them the other way round, the calculator will ask you to swap them around.
What is the difference between total days and years, months and days?
Total days is a plain count of the days between the two dates. Years, months and days express the same span in calendar units — whole years first, then whole months, then the days left over. For example, 26 years, 0 months and 0 days is the same span as 9,497 total days.