Age Calculator
Calculate calendar age between a date of birth and a selected as-of date.
What this calculator does
Calculate the calendar difference between a date of birth and selected date. The result is shown in years, months and days; choose another as-of date for a past or future event date.
How to use it
- Enter date of birth
- select as-of date
- calculate
- review years, months and days.
Formula and calculation method
Worked example
Important information
Calendar calculations account for month lengths and leap days. The selected as-of date should not be earlier than the date of birth.
Frequently asked questions
How accurate is this calculator?
It provides an estimate based on the values and assumptions entered. Verify important decisions with the relevant provider or a qualified professional.
Does this replace professional advice?
No. It is an informational tool and does not replace tax, legal, accounting, lending, investment or medical advice.
How calendar age is calculated
Calendar age is based on the difference between a date of birth and a selected “as of” date. The result is expressed in completed years, months and days, rather than by dividing the number of elapsed days by 365. This distinction matters around leap years and month lengths.
Use dates consistently
Check the day, month and year format before calculating, especially when entering dates from documents that use different regional formats. The result is a date-based calculation only; it does not determine legal age, eligibility or identity. Those decisions depend on the rules and records of the relevant authority.
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Browse all calculators AboutResults are estimates based on entered values and assumptions. They are not professional advice. Verify important decisions with the relevant provider or a qualified professional.