Age & Date Difference Calculator

Calculates exact age (years, months, and days), the real calendar difference between two dates, adds or subtracts time from a date, and the next birthday, using real calendar arithmetic — never a division of milliseconds by 365. Correctly handles months of different lengths, leap years, and births on February 29, with an explicit, selectable policy (February 28 or March 1) for non-leap years.

Processed on your device, no AI

The data is processed on your device and is never sent to the server.

Use cases

How to use this tool

  1. Choose the mode (age, difference, add/subtract time)
  2. Enter the required dates
  3. Copy or download the detailed result

Frequently asked questions

How does it calculate the age of someone born on February 29 in a non-leap year?
You can choose whether their birthday is considered February 28 or March 1 in non-leap years; the tool explains it and keeps the choice visible.
Does it use a 365-days-per-year approximation?
No. It calculates the real calendar difference (year, month, and day), which correctly accounts for months of different lengths and leap years.

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