Leapling Milly has only had two birthdays
26 February 2016 Last updated at 12:02 GMT
Imagine not being able to celebrate your real birthday every year.
Well that's what happens if your birthday is on the 29th February - a date which only happens during a leap year.
Every four years February has 29 days instead of 28 and people born on this day are known as leaplings.
We went to meet Milly to find out more about what it's like being a leapling. Check this out.