§1. The presbyterate is not to be conferred except on those who have completed the twenty-fifth year of age and possess sufficient maturity; an interval of at least six months is to be observed between the diaconate and the presbyterate. Those destined to the presbyterate are to be admitted to the order of deacon only after completing the twenty-third year of age.
§2. A candidate for the permanent diaconate who is not married is not to be admitted to the diaconate until after completing at least the twenty-fifth year of age; one who is married, not until after completing at least the thirty-fifth year of age and with the consent of his wife.
§3. The conference of bishops is free to establish norms which require an older age for the presbyterate and the permanent diaconate.
§4. A dispensation of more than a year from the age required according to the norm of §§1 and 2 is reserved to the Apostolic See.
Source: Code of Canon Law (Vatican.va)