🎈 Half Birthday Calculator

A half birthday is the date exactly half a year — 182 (or 183) days — after a birthday. In the US and UK in particular, it is a small tradition to mark a child's half-year birthday. Even outside birthdays, the same idea works for the "halfway point" of any recurring yearly date, such as a wedding anniversary or company founding date.

A year has 365 days (366 in a leap year), so the exact half is 182.5 days. Because of this, either 182 or 183 days is conventionally used as "half a year," and the two conventions differ by only about a day. This calculator uses 182 days as its default and notes that 183 days is also a common convention.

If this year's calculated half-birthday has already passed, the tool automatically moves to next year's birthday and its half-birthday, so it always shows a date that is still ahead along with the days remaining (D-day). It also estimates how many half-birthdays have been celebrated so far since birth.