Age Calculator
Find the calendar interval between a birth date and a reference date, with a clear leap-day convention.
Browser-based · No signup · Transparent assumptions
- 01Enter your values
- 02Adjust your settings
- 03Review your results
Enter your date of birth
Your exact age, birthday countdown, and life stats will appear here.
Calculations run in this browser. Shared URLs can contain input values. Review links before sharing financial, dietary or birth-date information.
When to use this calculator
Find calendar age on a chosen reference date or check when a birthday occurs. For a February 29 birth, compare the supported observation conventions; legal age rules can differ from the calendar convention selected here.
Review the worked example and assumptions below, then use the supported report or copy controls to keep the result with its inputs. Calculations run in this browser; a shared URL can include the values you entered.
How to use Age Calculator
- Enter the birth date and reference date.
- Choose February 28 or March 1 for leap-day anniversaries.
- Review the calendar age, total days and next birthday, then copy or export the result.
Calendar age versus elapsed time
Calendar years and months have different lengths. This calculator counts complete anniversaries, then complete months, then remaining calendar days. Total days use date-only arithmetic rather than local daylight-saving hours.
Worked example
Birth: 2000-01-15
Reference: 2025-02-20
Age: 25 years, 1 month, 5 daysAssumptions and limits
Birthday observation is a personal convention, not a legal age determination. Hours and seconds are calendar-day equivalents, not a measurement from a time of birth. Zodiac and generation labels are entertainment; the Chinese-year label does not account for Lunar New Year.
Reference: MDN: Date and UTC. Model/source review: 19 October 2026. See the tool-specific scope and precision limits above.
Frequently asked questions
Can I use a past reference date?
Yes. Choose any valid reference date on or after the birth date.
How are February 29 birthdays handled?
Select February 28 or March 1. The chosen convention applies to complete-year anniversaries and the next birthday.
Why are months not just days divided by 30?
A calendar month can contain 28 to 31 days. Complete calendar months give a different result from a fixed-day approximation.
A practical input scenario
Enter a birth date and an explicit reference date when you need a reproducible calendar-age result. Keep the selected date and birthday convention with your notes.
Read the scope alongside the result
Calendar-day equivalents do not measure elapsed time from a birth timestamp. Entertainment labels and birthday conventions are not legal determinations.