Calculate the time between dates, someone's age, or a date in the future.
Work out how long there is between two dates in years, months and days, calculate an exact age, count working days, or add and subtract time from a date — with the calendar's real irregularities handled properly.
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What Date Calculator supports
Compare
Days between two dates
Age calculator
Working days between dates
Arithmetic
Add or subtract time
Reference
ISO week number
Day of the year
About Date Calculator
Date arithmetic looks trivial and is full of traps. Months have different lengths, leap years arrive on a rule with two exceptions, and "one month after 31 January" has no obvious answer. Doing it by dividing by 30.44 gets you an approximation that is wrong often enough to matter.
This walks the actual calendar. Years and months are counted by stepping through real dates rather than dividing by an average, which is what makes "3 years, 2 months and 5 days" correct across leap years and months of different lengths.
Adding a month clamps rather than overflows: 31 January plus one month gives 28 February — or 29 in a leap year — rather than spilling into March. That is what almost everyone means, and it is what spreadsheet date functions do.
How to calculate between dates
1
Choose what you are calculating
The gap between dates, an age, working days, or a date in the future or past.
2
Pick your dates
Use the date pickers, or type a date directly.
3
Read the breakdown
You get years, months and days, plus the totals in days, weeks, hours and working days.
How leap years actually work
A year is a leap year if it divides by 4, except that century years are not, unless they divide by 400. So 1900 was not a leap year and 2000 was — a distinction that broke a surprising amount of software.
The rule exists because a solar year is about 365.2425 days. Adding a day every four years overcorrects slightly, and the century exceptions claw the difference back.
About working days
Working days here means Monday to Friday, excluding weekends. Public holidays are not deducted, because they differ by country and often by region — treat the figure as the maximum and subtract the holidays that apply to you.
Frequently asked questions
How many days are between two dates?
Enter both dates and you get the exact count, along with the same span expressed in years, months and days, and in weeks, hours and working days. The calendar is walked properly, so leap years and month lengths are handled.
How is age calculated?
By counting completed years, then remaining months, then remaining days from the birth date to the reference date. That is how age is conventionally stated, and it is why your age changes on your birthday rather than gradually.
What happens when I add a month to 31 January?
You get 28 February, or 29 in a leap year. The result clamps to the last day of the target month rather than overflowing into March, which is what people mean and what spreadsheet date functions do.
Are public holidays excluded from working days?
No, only weekends. Holidays vary by country and often by region, so the working-day figure is the maximum — subtract whichever holidays apply where you are.
What is an ISO week number?
The ISO 8601 week numbering used across Europe and in most business software. Week 1 is the week containing the first Thursday of the year, and weeks run Monday to Sunday — which means early January can fall in week 52 or 53 of the previous year.