How to use the age in days calculator
Enter your date of birth and optionally another date. The count starts at zero on the birth date.
How the calculation works
Days are measured between local calendar dates using UTC arithmetic, preventing daylight-saving time from adding or subtracting a day.
Check your inputs carefully: an incorrect date can change a result. Dates and times are entered using your device settings, and no account is needed. For formal, legal, medical or financial purposes, verify the applicable local rules and official records.
Frequently asked questions
Does today count as a full day?
The result counts full calendar-day boundaries elapsed since birth; birth day is day zero.
Does the calculator account for leap years?
Yes. AgeGlide uses calendar-based calculations and includes 29 February where applicable.
Are the dates I enter uploaded?
No. AgeGlide calculates your results in your browser. Entered dates are not sent to our server for processing.