Potty training a dog is a task requiring weeks, possibly months, worth of patience, diligence and consistency. Instinctively, dogs will not go potty where they sleep. This is generally taught to them by their mothers before they are given to their new family. Ultimately, there is no set time a dog will be trained by. It depends on his level of maturity, not his age. There are things you can do to help the process along, though.
Set a Schedule
To effectively potty train your dog, you need to get him on schedule. Feeding him at the same every day will help establish a consistent potty schedule. You should also set certain times of the day to take him outside--for example, take him out as soon as he wakes up from a nap, once he finishes eating and after he has played for 15 or 20 minutes.
Watch Him Closely
Potty training a new dog is extremely time consuming, mostly because you have to watch his every move. If your dog suddenly disappears or is sniffing around, he may be looking for a place to go potty.
Go Outside With Him
Sometimes people tie their puppy outside when it's time for him to go potty, but unless you observe him through the window the entire time, you won't know if he has actually done his business. Also, you need to take your dog to the same spot or location each time; he will smell his scent and learn that he is expected to potty there.
Each time your dog goes potty outside, praise him or give him a treat. Eventually he will associate the praise with his actions and will continue to potty outside.
Kennel (Crate) Training
Some people choose to use a crate to potty train their dog. Although using a crate for potty training is not much different from the tips mentioned above, you should not leave your dog alone in his crate for more than two or three hours a day. Puppies' bladders are small, so you will need to take your dog outside frequently, typically every 20 to 30 minutes. The more often you take him outside, the faster he will be potty trained.