33 years ago - Evan McCulloch is left on the doorstep of an Irish orphanage.
20 years ago - 13-year-old Evan runs away, living as a thief and street thug.
14 years ago - 19-year-old Evan fulfills his first contract kill.
10 years ago - 23-year-old Evan takes a contract on Animal Man's life. Buddy convinces him that he's wasting his talent as an assassin & that he could "do great things". He moves to Keystone City to become the new Mirror Master.
6 years ago - 27-year-old Evan is caught by Wally West. He is recruited by Amanda Waller for the Suicide Squad.
5 years ago - 28-year-old Evan escapes the Suicide Squad after Rick Flagg's death. He rejoins the Rogues.
The Silver Age versions of the Flash rogues gallery were almost entirely typified as a criminal who "invented a device' that allowed them to somehow completely violate the fundamental laws of physics... a burglar that invented a way to manipulate light with mirrors to the point where he was flat-out warping reality wasn't that much of a stretch. One of the main things we had to do with every classic member of the Rogues was to somehow explain just what the hell was going on.
Thankfully, at least with the second Mirror Master Evan McCulloch, a lot of the heavy lifting had already been done. (most notably by the guy that actually invented him. I'm not going to tell you who actually did it. You can probably just guess). It simply established that the original Mirror Master's equipment did the heavy lifting, and it was now being wielded by an Irish-born street thug & assassin. It wasn't a complex character shift, but it was an effective one. Once Mark Waid & later Geoff Johns started building Flash's Rogues into a truly menacing group by giving them an organizational structure, Evan was already in place and ready to kick ass. All they really did was play up his cocaine habit.
Evan is a really easy character to fit into our timeline. The main thing we did with him was also make him one of the earliest members of the Suicide Squad. He's just such an easy to understand character with such a utilitarian power that he fit in really nicely. It might seem like a bit of a stretch to keep reaching into the grab-bag of Flash villains for the Squad, but the fact is they're one of the best and most iconic group of bad guys outside of Gotham, and Mirror Master is one of the best.