We started a couple of weeks ago.
Barrett showed interest in the Elmo potty (that I returned) so when he mentioned it again...and again, I went back to the store and bought the potty.
We were home a few days so we set the timer and asked him periodically through the day to sit on the potty. After a week of that, he started feeling and recognizing the sensation and he started asking to sit on the potty.
We've now had more successes than accidents and he no longer wears diapers through the day. He still wears a diaper at night and a nap time but he's in big boy underwear the rest of the time.
Shopping is a little more fun because we have to pause for restroom breaks but I'm so proud that he can hold it through the store until we can find a restroom.
So proud of Barrett and his hard work to be a big boy!