What is a half birthday?
A half birthday is a date six calendar months after your birthday, roughly halfway between one birthday and the next. For example, someone born June 15 has a half birthday on December 15, while someone born December 25 has a half birthday on June 25. It's mostly a fun, informal milestone rather than anything official, though some families and schools celebrate half birthdays, especially when a child's actual birthday falls during a school holiday.
When is my half birthday?
To calculate your half birthday, add six months to your birth month and keep the same day of the month whenever that date exists. If adding six months takes you past December, continue from January. For example, a June 15 birthday gives you a December 15 half birthday, while a December 25 birthday gives you a June 25 half birthday the following year.
Some birth dates need a small adjustment because not every month has the same number of days. If you were born on the 29th, 30th, or 31st and the month six months later does not contain that day, the half birthday falls on the last day of that month. For example, someone born August 31 has a half birthday on February 28 in a non-leap year or February 29 in a leap year, rather than rolling over into March.
February 29 does not create the same problem. Six calendar months after February 29 is August 29, which exists every year. The regular birthday is different: February 29 does not occur in non-leap years, so this calculator lets you choose whether to count the next regular birthday as February 28 or March 1.
Frequently asked questions
How do I calculate my half birthday?
Add six calendar months to your birth date. If the corresponding day does not exist in the month six months later, use the last day of that month. For example, August 31 becomes February 28 in a non-leap year or February 29 in a leap year.
Is a half birthday a real, official date?
No — a half birthday is an informal tradition rather than a legally or officially recognized date. Some families and schools celebrate half birthdays, especially when a child's actual birthday falls during a school break.
Why does my half birthday land on a different day of the month sometimes?
Because not every month has the same number of days. If you were born on the 29th, 30th, or 31st, the month six months later might not contain that day. In that case, the half birthday falls on the last day of that month instead.