Enter a birth month and day to see how many days remain until the next birthday, the date and weekday it falls on, and the age being turned.
The calculation compares today's date with the next occurrence of the entered month and day. If that date has already passed this year, the following year is used; if it is today, the count is zero. A February 29 birthday is treated as March 1 in non-leap years, so the countdown always lands on a real date. When a birth year is given, the age being turned is the birthday year minus the birth year.
What happens for a February 29 birthday? In non-leap years the birthday is treated as March 1, so the countdown targets March 1 in those years and February 29 in leap years.
Is today counted if the birthday is today? No extra day is added. When the next birthday is today, the result is 0 days until the birthday.