How to use this calculator
Enter your date of birth using the date picker. The calculator defaults to today's date, but you can change the "Calculate to" date to find your age on any specific date, past or future. Results update instantly as you adjust either date.
The results panel shows your exact age broken down into years, months, and days, along with totals in months, weeks, days, and hours. You'll also see what day of the week you were born on and a countdown to your next birthday.
How date and age calculations work
Calculating exact age is more complex than simple subtraction because months have different lengths (28, 29, 30, or 31 days) and leap years add an extra day to February. This calculator handles all of those edge cases.
The algorithm works from the largest unit down: first it determines the number of full years, then the remaining full months, and finally the leftover days. For total conversions, it counts every single day between the two dates and multiplies to get hours and minutes.
Leap years occur every four years, except for century years that are not divisible by 400. So 2000 was a leap year, but 1900 was not. This matters when counting total days between dates that span many decades.
Frequently asked questions
How do you calculate exact age in years, months, and days?
Subtract the birth date from the target date starting with the day component. If the target day is smaller than the birth day, borrow from the previous month. Then subtract months (borrowing a year if needed) and finally subtract years. This approach correctly handles varying month lengths and leap years.
How many days old am I?
To find your total age in days, the calculator counts every calendar day between your date of birth and today, including leap days. A 30-year-old is roughly 10,950 days old, give or take a few days depending on how many leap years fell in that span.
What day of the week was I born on?
Enter your date of birth and the calculator instantly tells you the day of the week. This is computed using the JavaScript Date object, which implements standard calendar algorithms to determine the correct weekday for any valid date.
How do leap years affect age calculations?
Leap years add February 29 every four years (with exceptions for certain century years), so the total number of days between two dates varies. People born on February 29 only have a calendar birthday every four years. This calculator correctly accounts for all leap-year rules when computing totals.
When is my next birthday and how many days until it?
The calculator checks whether your birthday has already occurred this year. If it has, it counts the days until the same date next year. If it hasn't, it counts the days remaining until the upcoming occurrence. For leap-day birthdays in non-leap years, it uses March 1 as the next birthday date.