Birthday Calculator

Age calculation seems simple but has subtleties. In most Western countries, a person's age increases by one on their birthday each year. If someone is born on June 15, 1990, they turn 35 on June 15, 2025, and remain 35 until June 14, 2026. The calculation checks whether the current date has passed the birthday in the current year. If the current month is after the birth month, or if it is the birth month and the current day is on or after the birth day (or the month's last day, in a year when the month doesn't have the birth day), then the age is the year difference. Otherwise, subtract one year. Calculating exact days is more complex because months have different lengths (28, 29, 30, or 31 days) and leap years add an extra day. This calculator counts the actual calendar days from your birth date to the current date, leap days included, and gives the whole weeks and whole months in that span, a month too short to have your birth day ending on its last day. A birth day the month doesn't have (February 30, or February 29 of a common year) is taken as the month's last day, for the totals as for the age. Leap year birthdays (February 29) present a unique situation. People born on this date celebrate on either February 28 or March 1 in non-leap years, depending on personal preference and legal jurisdiction. This calculator counts the birthday on February 28 in those years, the month's last day, as MegaCalc's other date calculators do; some places observe March 1. Age reckoning differs across cultures. In some East Asian traditions, a person is considered one year old at birth and gains a year on the Lunar New Year, not their birthday. This means someone could be considered two years old by this system when they are only a few days old by Western counting.