About this half birthday calculator
A half birthday falls six months after a birthday, the point where someone becomes, say, 8½. It is popular for babies, for children whose birthdays fall in the holidays or over summer break, and for anyone who wants an extra reason to celebrate. The calculator adds six calendar months; when that day does not exist, the half birthday moves to the last day of the month, so 31 August becomes 28 or 29 February and 29 February becomes 29 August. Because months vary in length, the exact halfway point between two birthdays can be a day or two different, so both dates are shown.
How to find a half birthday
- Enter the birthday. Pick the date of birth and, if you like, add a name for the message. Press an example to try it.
- Choose a starting date. Leave Count from empty to use today, or pick another date to find the half birthday after it.
- Press Find half birthday. See the date, weekday, half age, and a live countdown, and compare the two counting methods.
Frequently asked questions
How do I work out a half birthday?
Add six months to the birthday. Someone born on 15 January has a half birthday on 15 July, and someone born on 10 November has one on 10 May.
When is the half birthday for 31 August?
February has no 31st, so the half birthday moves to the last day of February: 28 February, or 29 February in a leap year.
What about people born on 29 February?
Six months after 29 February is 29 August, which exists every year, so leap-day babies get a half birthday every year even when their real birthday is missing.
Why are there two different dates?
The calendar method adds six months. The exact midpoint splits the days between two birthdays in half, which can land a day or two away because months are not equal.
Do people really celebrate half birthdays?
Yes, especially for babies at six months and for children with summer or December birthdays, who often celebrate at school on their half birthday instead.