Dates & Time guide

How do I calculate my age?

Your age in full years equals the current year minus your birth year, then subtract 1 if your birthday hasn't happened yet this year. Born July 10, 1990, with today being July 4, 2026? That's 2026 − 1990 = 36, but July 10 hasn't arrived, so your age is 35. For age to the day, count the calendar days between the two dates.

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The Formula: Two Numbers and One Adjustment

The whole calculation rests on a single rule. Take the current year and subtract your birth year. That gives you a first-pass number. Then check the calendar: if your birthday hasn't arrived yet this year, subtract 1.

Work the example. Someone born on July 10, 1990, checked on July 4, 2026, gets 2026 − 1990 = 36. But July 10 is still six days away, so the birthday hasn't happened. Subtract 1, and the answer is 35. The moment July 10 arrives, they turn 36. The subtraction is the only part people forget, and it's why a raw year-minus-year figure is often one year too high.

Counting Age to the Day

Full years are the common answer, but sometimes you want more precision — age in exact days, or the breakdown into years, months, and days. For that, you count the actual calendar days between your birth date and today rather than just comparing years.

This is where doing it by hand gets tedious, because month lengths vary and the count has to hop across every February, April, and 31-day month in between. The Age Calculator handles the day-by-day arithmetic for you, so you can enter two dates and read off the exact span without tracking each month manually.

What Can Shift the Result

A few things quietly move the number. Leap years add a February 29, so any day count that crosses one picks up an extra day — and people born on February 29 only see their exact calendar birthday every four years. Time zones matter too: a birthday in one part of the world may not have started yet in another, which can flip the "subtract 1" decision by a day on the birthday itself.

Counting conventions differ by culture as well. In some East Asian age-reckoning traditions, a person is considered 1 at birth rather than 0, so the same birth date can produce a different number depending on the system being used.

Frequently asked questions

Why is my age one year less than the current year minus my birth year?

Because your birthday hasn't happened yet this year. The year-minus-year figure assumes you've already had your birthday; if you haven't, you subtract 1. Born in July and checking in January or June, you're still the younger number until July arrives.

How do I calculate my exact age in days?

Count the calendar days between your birth date and today, including every leap-year February 29 the span crosses. Doing this by hand means tracking varying month lengths, so an Age Calculator that counts date-to-date is the reliable way to get the exact figure.

How does a leap year affect my age?

A leap year inserts February 29, adding a day to any exact count that crosses it. People born on February 29 have a calendar birthday only in leap years, though their age in full years still increases every year.

Do all cultures calculate age the same way?

No. The year-minus-year method with the birthday adjustment is one convention. Some cultures count differently — for example, treating a newborn as age 1 rather than 0 — so the same birth date can yield a different age depending on the system.

Sources: AskANumber methodology.

Last reviewed July 4, 2026 · Editorial policy · This is general information, not financial advice.