Half birthday
How the half birthday calculator works out the date
By Toheed MehmoodReviewed How we check facts
In short
A half birthday is six calendar months after your birthday, on the same day of the month. Born 14 March, your half birthday is 14 September. If that day does not exist six months later, use the month's last day: a 31 August birthday has its half birthday on 28 February, or 29 February in a leap year.
- Half a year
- 6 calendar months
- Midpoint in days
- 182 or 183 days
- 31 August birthday
- 28 or 29 February
How to find your half birthday
- Enter your date of birth. The year only changes the age shown, such as turning 30½.
- Read the date of your next half birthday, its weekday and how many days are left.
- If you prefer an exact halfway point in days, use the midpoint shown under the main answer.
Half birthday for each birth month
| Birthday month | Half birthday month |
|---|---|
| January | July |
| February | August |
| March | September |
| April | October |
| May | November |
| June | December |
| July | January |
| August | February |
| September | March |
| October | April |
| November | May |
| December | June |
Birthdays on the 29th, 30th or 31st
Some months are too short. For birthdays from 29 to 31 August, the half birthday falls in February, which has 28 days, or 29 in a leap year. Birthdays on 31 March, 31 May, 31 October and 31 December land in months with 30 days. In each case the half birthday moves to the last day of that month.
| Birthday | Half birthday |
|---|---|
| 29 August | 28 February (29 in a leap year) |
| 30 or 31 August | 28 February (29 in a leap year) |
| 31 March | 30 September |
| 31 May | 30 November |
| 31 October | 30 April |
| 31 December | 30 June |
| 29 February | 29 August |
The exact midpoint between two birthdays
Six calendar months is not exactly half a year in days. The gap from one birthday to the next is 365 or 366 days, so the true midpoint is 182 or 183 days after your birthday, which can be a day away from the calendar half birthday. Both are fine; most people celebrate on the calendar date.
Why people celebrate half birthdays
- Children with summer birthdays celebrate at school, when classes are in session.
- People born close to big holidays get a day that is all theirs.
- Parents mark a baby's first six months.
- Couples and friends use it as an excuse for a small treat.
For the full countdown to your next real birthday, use the Birthday Countdown.
Common questions
When is my half birthday?
Six months after your birthday, on the same day of the month. The calculator shows the exact date and weekday.
When is the half birthday for 31 August?
28 February, or 29 February in a leap year, because February has no 31st.
What is the half birthday for 29 February?
29 August. That date exists every year, so leap-day babies always have a half birthday on the right day.
Is a half birthday exactly 182.5 days later?
Not always. Six calendar months can be 181 to 184 days. The exact midpoint between two birthdays is shown too.
Is a half birthday always six months after my birthday?
Yes. It falls on the same day of the month, six months later. If that month is shorter, as with 31 August, it moves to the last day of the month.
Why do people celebrate half birthdays?
Common reasons are a school celebration for children with summer birthdays, a baby's first six months, or an excuse for a small treat with friends.
Sources
- Gregorian calendar · Encyclopaedia Britannica
- What is a leap year? · Royal Museums Greenwich