A U-nn (e.g. U18) means that said player does not become older nn (e.g.18) years in the current year
For all age categories e.g. U16 category for an event in 2017, only players turning 16 years old on January 1st 2017 or after can register to this category.
We use January 1st as a cutoff for the remaining of the year to make it easier to calculate a player's age eligibility. We proceed the exact same way for our top national team competitions.
Color level applicable to age for U-nn is individual driven in all events other than national team, i.e. a U15 playing in U18 gets points for U15 irrespectively of playing in a U18 category.