Originally Posted by
Restingvoice
When he was 13-14. 6 months is the standard Robin training. Dick, Tim, and Jason trained in that amount of time. Tim got extra training with Lady Shiva after his 6 months were up.
Damian's been trained since birth so he's better than them at their age.
Duke took a year of training before Rebirth started, then maybe add a few months after Rebirth before he officially go out as The Signal after the first Metal, but that's when Rebirth runs in real-time.
Now though, since Damian only aged one year from Rebirth to Infinite, Duke's training naturally got shorter, but don't know how short. It's impossible to compress all of the Rebirth events into just one year anyway, but there ya go.
Steph in the new continuity is got a martial arts lesson before her story started (I think), then she was trained by Catwoman and her yakuza girlfriend, and then Nightwing sent her video training that she spent studying for half a year while the other Robins are saving the world, then under Batwoman during Gotham Knights. That was during the New 52-Rebirth publication in real-time though. Currently, I have no idea. New Steph is supposed to be the least experienced out of all Robins and Batgirls.