Are you allowed to go to an over 18 concert if you're 17 but your birthday is in less then 1 month?

Are you allowed to go to an over 18 concert if you're 17 but your birthday is in less then 1 month?
Of course because you have been in this world for 18 years and your birthday is less than 1 month so it counts that you are 18 years old :)