Birthday Difference Calculator
Compare two birthdays, their exact age gap, weekdays and calendar-day separation.
Compare two birthdays
See both the exact birth-date gap and how far apart the birthdays fall in a calendar.
Two useful comparisons
This tool separates two ideas: the full elapsed age gap between dates of birth and the distance between the recurring calendar birthdays. People with a large age gap may still celebrate birthdays only a few days apart.
Privacy
Input values are processed by JavaScript in your browser. The calculator code does not submit them to a server or place them in the URL.
Frequently asked questions
What is calendar birthday separation?
It is the shortest number of days between the month-and-day combinations on a leap-year calendar, ignoring birth year.
Why use a leap-year calendar?
It allows February 29 to be represented consistently.
Can the weekdays change each year?
Yes. The displayed weekday is the weekday of the original entered date.