Half-Birthday Calculator
Find a half-birthday from any birth date. Enter the date of birth and the calculator shows the exact half-birthday, six calendar months after the birthday, along with the next date it falls on, the weekday, and how many days are left until then. Leap-day births and month-end overflow are both handled correctly. Free and instant in your browser.
Find your half-birthday, the date exactly six months from your birthday. Enter a date of birth and the calculator shows the half-birthday, the next time it comes around, the weekday, and the days left until then. Leap-day births and month-end cases are handled. It answers when is my half-birthday for any birth date.
- Leap-year accurate
- 100% free
- No sign-up, no app
- Instant as you type
- Works offline after first load
How to use it
- 1
Enter the date of birth
Pick the birth date. The half-birthday updates straight away.
- 2
Read the half-birthday
See the date six calendar months on, and the next time it comes around from today.
- 3
Plan around it
Use the days-to-go figure to time a surprise, a card or a half-birthday treat.
When it comes in handy
Kids' half-birthdays
Mark a child's half-birthday, popular for summer-born children whose real birthday falls in the school holidays.
Surprises and treats
Plan a low-key celebration halfway to the next birthday, with time to prepare.
Classroom celebrations
Work out half-birthdays for children whose birthdays fall outside term time.
Instant, accurate & 100% in your browser
The calculation runs right here in your browser, counting the real calendar so leap years and month lengths come out right. Nothing you type is sent to a server, there is no sign-up and no limit, and once the page has loaded it keeps working even with no connection.
Frequently asked questions
- How is a half-birthday calculated?
- This calculator uses the "plus six calendar months" convention: the half-birthday is the same day of the month, six months after the birthday. So a birthday on 20 May gives a half-birthday of 20 November. This lands on a fixed calendar date, unlike adding 182 or 183 days, which can drift by a day across leap years.
- What is the half-birthday of a 29 February baby?
- A 29 February birthday gives a half-birthday of 29 August. August always has 29 days, so there is no clamping needed, and a leap-day baby gets a clear half-birthday every single year even though their real birthday only lands every four years.
- What happens when the birthday is at the end of a long month?
- When the target month is shorter, the half-birthday is clamped to that month's last day. A birthday on 31 August is six months from February, which has no 31st, so the half-birthday falls on 28 February, or 29 February in a leap year. The calculator shows the exact date for the year in question.
- Why do people celebrate half-birthdays?
- Half-birthdays are popular for children whose real birthday lands in the school holidays or close to Christmas, so they miss out on a class or family celebration. Marking the date six months away gives them a moment during term time. Plenty of adults use them too, as a light excuse to celebrate halfway through the year.
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