1. He gets up at six-thirty every morning.
2. He gets up at six thirty every morning.
(Which one is right? Do we have to use a hyphen or not?)
#1 is correct. Yes, the hyphen is needed.
http://grammar.ccc.commnet.edu/grammar/marks/hyphen.htm
Both versions are grammatically correct, but they have slightly different meanings.
1. "He gets up at six-thirty every morning."
In this sentence, the use of a hyphen indicates that "six-thirty" is being used as a compound adjective to modify the noun "morning." The hyphen helps to clarify that the time "six-thirty" is functioning as a single unit.
2. "He gets up at six thirty every morning."
In this version, there is no hyphen between "six" and "thirty." Without the hyphen, "six" and "thirty" are read as separate words.
Both versions are commonly used, so the choice between using a hyphen or not ultimately depends on writing style or personal preference. However, when wanting to express the time as a compound adjective and clarify its unity, using a hyphen (like in the first version) is generally recommended.