Chronos is the archenemy of The Atom. His main power is time travel he almost always uses this power and sometimes he will go to the future and the past with his opponents to trap them, he also used alot of gadgets and traps. He developed his time travel power from prison; he synchronized all of his movements and actions by the click of the clock that was in prison. He got his powers from the time he spent in prison.

The first time he was defeated was by Atom in Ivy Town.

He appeared in Justice League Unlimited in the episode "The Once and Future Thing". In this episode he was even more determined to get it to work, beacuse his peers shunned his "ludicrous" ideas of time travel. Now able to go back and forth through time, David took small, priceless objects that wouldn't' be missed (Cleopatra's comb and the first draft of the Magna Carta being two of them).

When his (verbally) abusive wife, Enid, begins chastising him for stealing such trivial things, Chronos jumps back into the past once again...this time to steal Batman's utility belt.

When the Watchtower alarm sounds, Batman, Green Lantern and Wonder Woman rush to investigate; digging into Batman's wall, Chronos finds Batman's utility belt, but not before they arrive on the scene. Worried that they saw him, Chronos opens a time portal once again and is thrown back into the past--June 12th, 1827 to be exact. Though the portal opened and Batman, Green Lantern and Wonder Woman were only a few seconds behind, Chronos landed six months ahead of them, robbed of his belt, jailed and held under the command of Tobias Manning.

The League came to free another jailed man, Bat Lash, when they saw David in the cell next to him. Claiming he wanted nothing more than to go back home and forget all of this, David gets them to get his belt back from Tobias. While Batman inspects it, David hits a switch which sucks him into the future; the League follows him.

In the future, the League finds that he's completely warped it; bringing people that were dead back to life, going in the past and preventing others from being born and people randomly appearing out of nowhere. Attempting to not be the "worthless" man that Enid and her mother scolded him for being, Chronos ruled the future, taking down the majority of what was once the Justice League Unlimited.

Chronos attempted to go back into the past, at the beginning of time, to start fresh and anew. Green Lantern and Batman had stopped him right before he could start everything. Installing a program into his belt, Batman put Chronos into a never-ending loop, with his wife yelling at him over and over and over and over again...