Date & time · Birthdays
Half birthday calculator.
Your half birthday is six months after your birthday. Enter your birth date to see the next one and how long you have to wait.
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How to find your half birthday
Add six months to your birth date, keeping the day of the month. Born 15 March, the half birthday is 15 September. There is no official rule for it; this is the usual everyday meaning.
Worked example. Born 15 March 1990, counting from 8 October 2026: the next half birthday is Wednesday, September 15, 2027, 342 days away, when you are 37.5.
Short months. If six months later has fewer days, the tool uses the last day of that month. Born 31 August 1990, the half birthday lands in February, so the next one counted from 8 October 2026 is Sunday, February 28, 2027 (143 days away), when you are 36.5.
Frequently asked questions
What is a half birthday?
The date exactly six months after your birthday, when you are a half year older than your last birthday. It is used informally, for example to mark a baby's six-month point.
How do I calculate my half birthday?
Add six months to your birth date and keep the day. If that day does not exist in the target month, use the last day of that month.
Is there an official half birthday date?
No. It is an informal convention. This tool uses calendar months.
What if I was born on February 29?
Your half birthday is August 29, which exists every year.
Method
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Calendar arithmetic only. No external data.
Runs entirely in your browser. Nothing you type is sent or stored.
Scope
For information and fun only. Not legal, medical or genealogical advice; rules about ages, eligibility and family relationships vary by place and program.