Updated
Age Calculator
Your age in years, months, and days is the calendar distance from your date of birth to today. This calculator counts whole years first, then whole months, then remaining days. It also tells you exactly how many days remain until your next birthday.
Skip to the calculatorEnter your date of birth to see your exact age in years, months, and days.
Enter your date of birth to see your exact age in years, months, and days.
How exact age is counted
Age counts whole years first, then whole months, then remaining days. When the current day of the month is smaller than the birth day, days are borrowed from the month before the as-of date. Because months have different lengths, this is a convention, not a law of arithmetic, and different calculators pick different conventions.
Example of the ambiguity: from January 31 to March 1, one convention counts "1 month and 1 day" (Jan 31 → Feb 28 is a month, plus a day), another counts "29 days" (Jan 31 → Mar 1 directly). Both are defensible. This page states its convention openly so the result is reproducible.
Leap-day birthdays
Around 1 in 1,461 people are born on February 29. In common years this calculator counts their birthday as March 1, the first day after a full year of life has passed. Legally, jurisdictions differ: New Zealand rounds to February 28, most US states to March 1.
What day of the week was I born?
The calculator names it above. Weekdays are worked out on the proleptic Gregorian calendar, the one in use today projected backwards. For dates before its adoption in 1582 the answer is arithmetically consistent, but it is not the weekday people recorded at the time, because the Julian calendar was still in force.
How many days have I been alive?
The result lists your age in days, weeks, hours, minutes and seconds. Those are conversions of whole calendar days: this calculator asks for a date, not a time of birth, so the hour and second figures are exact multiples of days, not a true count of elapsed time since you were born.
Days in each month
| Month | Days |
|---|---|
| January | 31 |
| February | 28, or 29 in a leap year |
| March | 31 |
| April | 30 |
| May | 31 |
| June | 30 |
| July | 31 |
| August | 31 |
| September | 30 |
| October | 31 |
| November | 30 |
| December | 31 |
A leap year is every year divisible by 4, except century years, which must be divisible by 400. So 2000 was a leap year and 1900 was not.
Age systems in other cultures
This calculator uses the Western system: you are 0 at birth and gain a year each birthday. The traditional East Asian system counted a person as 1 at birth and added a year each New Year; South Korea officially switched to international age in 2023.
Frequently asked questions
How is age calculated exactly?
Count whole years from the birth date, then whole months, then remaining days. When the day of the month is smaller than the birth day, days are borrowed from the month before the current one. Month lengths differ, so two people can have the same age in days but different ages in months and days.
What if I was born on February 29?
In common years this calculator counts your birthday as March 1. You complete a full year of life once February ends. In leap years your birthday is February 29 as normal.
Why do different age calculators give slightly different answers?
Month-end edge cases have no single convention. Example: from January 31 to March 1, some tools count 1 month 1 day, others 29 days. This page states its convention: days borrow from the month before the as-of date.
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Written by the CalculatorJam editorial team. Formulas and edge cases are documented on this page and verified by automated reference tests. Last updated . Read our editorial policy.