Across the armed forces, the minimum age allowed for enlistment is 17 (with parental consent) and 18 (without parental consent). The maximum age for enlistment for someone who has never served in the military before varies by branch; for the Army it's 35, for the Navy it's 34, for the Air Force it's 39 and for the Marines it's 28.
The year of the horse means there is leadership associated with this sign this year, so your authority may increase, according to Ng. However, the impulsive behaviour of the horse can lead to recklessness, so stay away from gambling and speculations.
A yearling. A yearling is a young horse of either sex that is between one and two years old. Yearlings are comparable in development to a very early adolescent, they are not fully mature physically, and while they may be in the earliest stages of sexual maturity, they are considered too young to be breeding stock.