As I said in the previous post, foals start eating solid food very quickly indeed.
Full weaning - when the foal no longer attempts to suckle and is no longer allowed to - takes longer. Typical natural weaning is 10-11 months - right before a wild mare drops her next foal. A mare who has not caught again, though, may let her foal nurse occasionally up until 2 years or so.
Domestic horses are, of course, often weaned sooner.