How the age calculation works
The calculator compares calendar dates, borrowing days from the previous month when needed. It reports completed years, remaining months, and remaining days. The “next birthday” count uses calendar days and does not account for time of birth or time zone.
How to read date differences
The date-difference tool counts full calendar-day intervals. For example, the interval from Monday to Tuesday is one day. It does not count both endpoints as full days; if you need an inclusive count for a schedule, add one to the result where appropriate.
For legal age, deadlines, travel documents, benefits, or official forms, follow the relevant agency’s date and time rules.
Date calculator FAQs
Does age update automatically?
The result uses the “Age as of” date shown in the form. Change that date to calculate age on another day.
Does date difference include the start date?
It counts the elapsed calendar-day interval between dates. It is not an inclusive count of both start and end dates.