Birthday Calculator
Enter a birth date and an as-of date to calculate calendar age and the next birthday locally.
Birthday calculation
- Calendar age
- Next birthday
- Days until next birthday
Dates use your local calendar date. February 29 birthdays use February 28 in non-leap years.
A QUICK WALKTHROUGH
How to use this tool
- Enter a valid birth date.
- Choose the date on which to calculate.
- Review calendar age and the next birthday countdown.
Calendar dates
Dates are interpreted as calendar dates in your local time zone. The calculation does not use the current clock time.
Leap-day birthdays
For a February 29 birth date, the next birthday is treated as February 28 in a non-leap year. Age remains calendar-based.
Local processing
Dates are processed only in this browser and are not uploaded or stored.
GOOD TO KNOW
Common questions
Can I calculate age on a past date?
Yes. The as-of date may be any valid date on or after the birth date.
How is February 29 handled?
In a non-leap year, the next birthday is February 28.
Does this use my time zone?
Yes. The date fields are calendar dates in your local time zone; the clock time is ignored.