Does the calculator work for dates before 1582?

Yes. It uses the proleptic Gregorian calendar, which extends the current leap year rules backward. This is standard for historical age calculations, though people living before 1582 used the Julian calendar, which had different leap year rules.

What happens if I was born on 29 February?

The calculator handles this correctly. On non-leap years, your age in completed years increments on 1 March, the conventional treatment. Your exact age in days, hours, and seconds continues to accumulate normally.

Why does my age in days not match years times 365?

Because of leap years. Multiplying your age by 365 ignores the extra day in each leap year. Over 80 years, that shortcut misses about 20 days. The calculator counts each actual day.

Can I calculate someone else's age?

Yes. Enter any valid birth date and, optionally, birth time. The tool works for any person, living or historical. No login or account is needed.

Does the calculator account for time zones?

No. Age is date-based, not time-zone-based. Your age in completed years, months, and days is the same everywhere. If you enter a birth time, the calculation uses the time as entered: it does not convert between time zones. For exact hour calculations, use the time zone where the birth occurred.

Age Calculator

A child born on 29 February will celebrate only about 20 actual birth anniversaries by age 80. That single quirk of the Gregorian calendar shows why "subtract the birth year from this year" fails so often. If your own celebration falls in December and the month is July, you are still a full year younger than that shortcut suggests. The correct answer is your chronological age: the exact time elapsed since your birth, measured in completed years, months, and days.

How old am I in completed years, months and days?

This tool calculates chronological age: the time elapsed since birth, using the Gregorian calendar. It answers "How old am I right now, in completed units of time?" It does not estimate, round, or average. The output is your age at your last celebration (completed years), plus the additional months and days since then.

How an exact age calculator handles leap years and month lengths

Leap years and variable month lengths make age calculation non-trivial. A person born on 1 March 2020 turned one on 1 March 2021: 365 days later. A person born on 1 March 2019 turned one on 1 March 2020: 366 days later, because 2020 was a leap year. Both were one year old on their anniversary, but the day count differed.

The calculator uses the standard JavaScript Date object, which correctly handles the Gregorian leap year rule: years divisible by 4 are leap years, except century years not divisible by 400. So 1900 was not a leap year. 2000 was. For dates before 1582, the tool uses the proleptic Gregorian calendar, extending the same rules backward. This matters for genealogical or historical age calculations.

Calendar months also vary. January has 31 days. February has 28 or 29. April has 30. The calculator accounts for each month's actual length. It does not assume all months are 30 days or that a year is exactly 365 days.

How do I enter my birth date and time?

You need your birth date. The calculator also accepts an optional birth time. Without a birth time, the tool calculates your age based on the date only: your age in completed years, months, and days resets at midnight on the anniversary of your birth. With a birth time, the calculation becomes exact to the hour, minute, and second. If you were born at 3:14 PM on 20 July 1990, the tool can tell you that you turned exactly 36 years, 4 months, and 12 days old at 3:14 PM on 2 December 2026.

Understanding the results: years, months, days, hours, seconds

The primary output is your age at last anniversary: the number of full years you have completed. This is the standard everyday meaning of age. Below that, the calculator shows the additional months and days since that anniversary, and if you entered a birth time, the hours and seconds since that moment.

The total outputs (total days alive, total hours, total seconds) use the Gregorian average year of 365.2425 days for conversions. For reference: 70 years equals about 25,567 days. 80 years equals about 29,219 days. 90 years equals about 32,872 days. These figures assume an average year, not your actual anniversary count, which may differ by a few days depending on how many leap years you have lived through.

Does an exact age calculator keep my data private?

All computation happens in your browser. No birth date, birth time, or any other personal information is sent to any server. The page works without an internet connection after loading. Your exact age is personal data. This tool does not collect, store, or transmit it.

When exact age matters: legal, medical and personal uses

Exact chronological age is not a curiosity. It determines:

Pension eligibility: many schemes specify eligibility by years and months, not just birth year.
School enrolment cutoffs: a child must be exactly 5 years old by a specific date.
Clinical trial enrolment: age ranges are often specified to the day.
Insurance underwriting: some policies use age at last anniversary. Others use age at nearest anniversary. Some use age next birthday. The convention varies.
Genealogical research: exact age at death is needed for accurate family trees, especially across calendar changes.

For a deeper look at the mechanics, see the articles on how age calculators handle leap years and how to calculate your exact age manually. If you need the count of total days lived, the days-old calculator covers that separately.

Quick reference: completed age at milestone years

Milestone	Approximate days	Approximate hours
70 years	25,567 days	613,608 hours
75 years	27,393 days	657,432 hours
80 years	29,219 days	701,256 hours
85 years	31,046 days	745,104 hours
90 years	32,872 days	788,928 hours

Based on the Gregorian average year of 365.2425 days. Your actual day count may vary by a few days depending on the leap years you have lived through.