The Mathematics of Birthday Days of the Week
Because a standard solar calendar year has 365 days, and \(365 \div 7 = 52\) with a remainder of 1, your birthday normally advances by one day of the week each year.
However, whenever a leap year with 366 days occurs (\(366 \div 7 = 52\) with a remainder of 2), your birthday will jump forward by two days of the week if your birthday occurs after February 29. Check our Leap Year Calculator to verify which years introduce this leap jump.
Curious about your exact age down to the second? Try our comprehensive Age Calculator.