Dates
Age & Date Calculator
Three date tools in one: an exact age in years, months and days; the full duration between any two dates including weekday and weekend counts; and a date calculator that adds or subtracts days, weeks, months or years.
Four steps
How to calculate an exact age
- 1
Pick a mode
How old for an age, Between dates for a duration, Add/subtract for date arithmetic.
- 2
Enter the date of birth
Type or pick the date — the result updates as you go.
- 3
Set the reference date
Leave it as today, or change it to work out age on any other date.
- 4
Copy the result
Use the copy button to take the formatted answer into a form or document.
Why “365.25 days a year” gives the wrong answer
The quick way to calculate an age is to subtract the two dates, divide by 365.25 and round down. It is close, and it is wrong often enough to matter — particularly around birthdays, leap years and February. Someone born on 1 March 2000 is not 25.0027 years old; they are 25 years, 0 months and 1 day, and on a form that difference can decide eligibility.
This calculator works the way a registrar does: count whole years, then whole months, then the days left over, borrowing the correct number of days from the preceding month when the day of the month has not yet arrived.
What each mode is for
- How old — exact chronological age. Used for school year placement, medical dosing charts, sports age groups, insurance and visa forms.
- Between dates — project durations, notice periods, tenancy lengths, how long until an event. The weekday count is the useful one for working days.
- Add / subtract — deadlines and due dates. “Ninety days from today”, “six weeks before the wedding”, “two years after signing”.
Chronological age and why it is used
Educational assessments, speech and language reports and developmental screening tools all require a chronological age expressed in years and months — sometimes years, months and days. It is normally calculated on the date of testing, which is why the reference date here is editable rather than locked to today.
Working days versus calendar days
When a contract says “within 30 days” it usually means calendar days; when it says “30 working days” it means Monday to Friday, excluding public holidays. This tool gives you both the calendar total and the Monday-to-Friday count, but it cannot know your country’s public holidays — subtract those yourself using a printed calendar for the months involved.
Related tools
The calendar generator prints any month of any year, the planner turns a deadline into a schedule, the percentage calculator covers proportional maths, and the unit converter handles measurement conversion.
Answers