Age Calculator: Frequently Asked Questions

For people born on February 29, the calculator uses February 28 as the birthday in non-leap years for the purposes of calculating days until the next birthday and counting complete years.

The calculator uses date-level precision (year, month, day) rather than time-of-day precision. For most purposes this is sufficient. If the exact time of day matters (e.g., you were born at 11 PM and it is currently before midnight on your birthday), the calculator may show 0 days until your birthday when technically you have not reached the birth time yet.

Yes. Enter any start date (a company founding date, a building construction date, an investment start date) and a target date. The result gives the exact age of anything with a known start date.

The calculator uses calendar month boundaries. A month is counted as complete when the same day of the month is reached in the next month (e.g., Jan 15 to Feb 15 = exactly 1 month). Partial months are counted as the remaining days after complete months are subtracted.

There is no practical upper limit. The calculator can compute the age of historical figures, ancient buildings, geological formations, or the universe itself (approximately 13.8 billion years). For very large dates, precision may be limited by the JavaScript date object's range.

Yes. Change the target date from today to any past or future date. This lets you find how old someone was on a specific date in the past, or how old they will be on a future date.