36 months. Wait till he is old enough to ask for it.
18-24 months. Babies should not have candy. But when older, perhaps about 18-24 months old, and if the toddler has good eating habits already, he can have a little baby-safe candy if the family is enjoying some candy together.
Choking Hazard. Most hard candy is a choking hazard until three. Even then, keep those teeth in mind. They are certainly easy to get cavities at this age. Sparingly!
Not before 2 months. It's not a good idea to introduce junk food (candy, soda, etc) early-- why get a baby used to those tastes and craving junk? Hard candy itself is a special hazard, as it can cause choking and death. Please, no candy for babies!