I read from Parenthood previously, that best time to potty time is when 24-27mths. Less effort & save time! But, it's all depends to your kid(s) whether are they ready not. Do observe their body language that able to tell you. Too much pressure or wrong method use might make delay the potty train.
TRUE!! alot of my frens' kids are still wearing diapers even @ 3. the best time to teach is when they recognize their own body parts and know wat they're doing!!