Is it ever established how long into Bruce's career as Batman the first episode of BTAS is?

Like, how long has he been Batman by the start of "On Leather Wings"? The Joker and the Penguin are established, but every other classic Rogue gets an intro episode. Harvey's also not Two-Face yet and becomes him over the course of the first season.

Yet clearly it's not right at the very beginning, because in "Robin's Reckoning" we see flashbacks to Batman in a more Year One-type suit, wiith a more primitive belt and no yellow oval around the bat symbol.