Calculators
Age Calculator Between Two Dates
Enter two dates — a start date and an end date — to calculate the exact difference in years, months, days, weeks and total days.
Calculate age between two dates
Results
Enter valid values to see results.
About this tool
This is an age calculator between two dates. The first date is the start (usually a date of birth). The second date is the end (today by default, or any date you pick). The result is the exact calendar span in completed years, months and leftover days, plus total weeks and total days — not “number of days ÷ 365”.
How to use
- Enter the start date in “Date of birth (start date)”.
- Enter the end date in “Age as of date (end date)”, or leave it as today.
- Read years, months, days, then total months, total weeks and total days.
Formula and methodology
Years, months, and days are computed according to civil calendar conventions: if the end day-of-month is less than the birth day-of-month, one month is borrowed from the previous month and the actual number of days in that previous month is added to the day count. If months go negative, one year (12 months) is borrowed. Total days use the exact midnight date difference, and total weeks are total days divided by 7 (discarding remainder).
Worked example
Born on 15 March 2000 and measured on 15 September 2026 is exactly 26 years, 6 months, and 0 days. The same span equals 318 completed months, 1,382 weeks, and 9,680 days.
Frequently asked questions
Can I calculate age between two arbitrary dates?+
Yes. Put the earlier date in “Date of birth (start date)” and the later date in “Age as of date (end date)”. The result is the exact calendar difference, not an estimate from 365-day years.
Is this only a “how old am I today” calculator?+
No. Today is just the default end date. Change the second date to get age on a birthday, a visa deadline, or any other day — the same years / months / days / weeks / total days breakdown.
How are leap years and February 29 handled?+
February 29 is treated as a real calendar day. If born on February 29, the calculator uses the actual month length of February (28 days in common years, 29 in leap years) to determine completed years, months, and days.
Why do total months match (years × 12 + leftover months)?+
Total months counts completed calendar months rather than dividing total days by an arbitrary 30 or 30.4 days, ensuring exact calendar consistency.
What happens if the reference date is before the birth date?+
The calculator requires the reference date ('Age as of date') to be on or after the date of birth, and displays a clear message if dates are inverted.
Guides
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