Age in Days
An elapsed calendar-day total
Age in Days counts the actual calendar-day boundaries between the birth date and the calculation date. Leap days are included automatically because the calculator uses the real dates rather than multiplying years by an average number of days.
The result is an elapsed-day count: on the birth date the total is zero, and after one full calendar day it becomes one. That convention avoids adding an extra day simply because both endpoint dates are visible on the calendar.
Why a day is not always 24 elapsed hours
Day totals are useful for milestones and comparisons, but they are not the same as age in hours. A local daylight-saving change can make a civil day 23 or 25 clock hours long; this page intentionally keeps the calendar-day count stable across those transitions.
Questions people ask
Does this account for leap years automatically?
Yes — it counts the actual calendar days between the two real dates, so every real leap day in between is already included.