What does this mean: Contest open to entrants ages 13-18 only.?

Do i have to be between 13-18 years or is it ok to be above 18 (18+)?

I'm from the Netherlands and it's quite confusing. Thanks for the answers.

Kiteman4 years ago
You must be *below* 18 to enter.

Aged 13, 14, 15, 16, 17, 17yrs and 11 months, OK.

Aged 18, not OK
what about 17 years 11 months 30 days 23 hours 59 minutes and 59 seconds.
Doesn’t cut butter in February and a few others:-D