How this calculation works
The date of birth is compared with the selected as-of date using calendar-aware arithmetic. The next birthday is then found after that date.
Formula used
Exact age = calendar difference between date of birth and as-of date.
Practical example
Someone born on 10 June 1995 is 30 years old on 10 June 2025, with 360 completed months.
Important considerations
- The as-of date cannot be before the date of birth.
- Documents may use a specific cut-off date.
- Time of birth is not considered.
Frequently asked questions
Can I calculate age on a past date?
Yes. Choose any as-of date on or after the date of birth.
How are leap-day birthdays handled?
Calendar rules are used; the next valid birthday date is calculated by the browser.
Disclaimer
This free tool provides an estimate for general information only. It is not official financial, tax, payroll, employment or legal advice. Rules and employer policies can change; verify the result with the relevant authority or a qualified professional before making decisions.