When is my half birthday? Six months after your birthday, worked out exactly

How to use the half birthday calculator

1. Enter the Date of birth.
2. Count from is filled in with today’s date (taken from the UTC calendar, so it may show the wrong day close to midnight). Change it to plan from another date.
3. If the birthday is on a day that the month six months later lacks, choose Last day of the month or Roll into next month.
4. Read the Half birthday day and month, the Next half birthday with its weekday, Days until it, the half-age You will be, and the First half birthday.

What it does and when to use it

Half birthdays are a fun extra celebration, and a practical one for anyone whose real birthday falls on a holiday. Children born near Christmas or in the summer break often mark the half birthday at school instead. Families also use it for “half-year” photos of babies and for a mid-year treat.

If you want the full count to your next real birthday, use the days until calculator with “Repeats every year” ticked. The age calculator gives an exact age in years, months and days. For more birthday fun, look up your zodiac sign or your Chinese zodiac animal.

How it works

The tool adds six calendar months to the date of birth to get the first half birthday. It then adds 12 months at a time until it reaches a date on or after the Count from date. When the target month is too short, it either uses the last day of that month or rolls the extra days into the next month, as you chose. The age shown is the number of whole years you have lived on that date, followed by ½. All the maths is done with calendar dates, so time zones cannot shift the result by a day.

Worked examples

All three count from 7 October 2026.

Born 29 August 2008, last-day option. Six months later is February, which has no 29th in 2027, so the result is Next half birthday: Sunday, 28 February 2027, 144 days away, at age 18½. A note explains the adjustment. In a leap year such as 2028, the half birthday falls on 29 February.

Same birthday, roll-over option. The missing day carries into March: Next half birthday: Monday, 1 March 2027, 145 days away.

Born 10 April 1999. The half birthday is 10 October, so Days until it: 3. That Saturday they turn 27½.

Limits and tips

• If the Count from date is the half birthday itself, the days line shows “Today”.
• For a newborn’s six-month mark, the First half birthday line gives the exact date.