Age Difference Calculator

How the age difference calculation works

The gap between two birth dates is a fixed number — it never changes, no matter when you measure it, because both people age at the same rate. This calculator finds it two ways. First, the total days apart: both dates are converted to a day count (using UTC, so daylight saving time can't add or steal an hour) and subtracted. Second, the calendar difference in years, months, and days, worked out by subtracting the dates column by column — days first, then months, then years — and borrowing the correct number of days from the preceding month whenever the day column goes negative. That borrow step is why "5 years, 6 months" style answers can differ by a day or two between calculators that skip it.

Each person's current age is shown the same way, measured from their birth date to today. If both birth dates are identical, the difference is zero — same age, born the same day.