Age in Days Calculator

Calculate your exact age in days, weeks, months, years, hours, minutes, and seconds. Perfect for milestones and celebrations.

This calculator converts two calendar dates -- a birth date and a current or reference date -- into elapsed time. It builds both dates from Year, Month, and Day fields and takes the plain difference between their timestamps in milliseconds, then divides by the length of a day to get Age in Days (line 19); every other unit is derived straight from that single day count rather than recalculated independently. Age in Weeks divides the day count by seven, Age in Hours multiplies it by 24, and Age in Minutes and Age in Seconds keep multiplying from there (lines 20 and 23-25) -- so all four track Age in Days exactly and will never disagree with it. Age in Months and Age in Years are the two exceptions: instead of counting real calendar months and years the way a birthday-borrowing calculation would, they divide the day count by two fixed averages, 30.44 days per month and 365.25 days per year (lines 21-22), the long-run average including leap years. That means Age in Years from this calculator can differ by up to a few days' worth of rounding from a birthday-based age calculation for the same two dates, especially near a birthday. Current Year, Current Month, and Current Day default to today's date but can be set to any date, letting the calculator measure the gap between any two dates, not just age from a real birthday. It does not validate that the day you entered exists in the month you chose -- JavaScript's own date handling rolls an out-of-range day into the following month automatically, rather than the calculator rejecting it.