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 as well as the past with his opponents to trap them, and uses a variety of gadgets to do it. 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.
When introduced in the 60’s, Gil Kane based David Clinton’s face on former vice president Richard Nixon.
Choi begins to realize that prolonged usage of the Atom belt can cause one to shrink. Choi fears he will lose equilibrium unless he finds the source of this anomaly in his blood. Choi calls in Panda Potter to help with this endeavor. Choi has developed a diminution mapping engine that will enable him to observe the nucleus of his blood cells. Choi primarily wants to investigate the white corpuscles for any signs of radiation poisoning or tachyons since the belt has endured temporal exposure from dimensional rifts.
Unfortunately, the mapping engine was miscalibrated and Choi's blood sample became a matter displacing rift. Potter tells Choi to run before got sucked into the rift. Choi didn't want to but he knew that Potter trusted him in finding an answer to stop the rift. Choi exits his house but the rift continued to expand in size. As Choi takes a moment to breath, he is approached by city council member Matt Wilson who has brought a news crew with him. Wilson confronts Choi about his involvement with Ivy Town's recent chaos for the past couple of months. Before Choi could answer, the rift swallowed his home and made its way to his next door neighbor Amanda.
Choi makes his way through Amanda's home and finds her holding for dear life as the vacuum of the rift increases. Wilson and the news crew are sucked into the portal and Choi tries to maintain a firm grasp of Amanda but it wasn't enough. Amanda falls into the portal and Choi follows in after her. For a moment Choi was unconscious then he wakes up and finds himself floating on a hunk of wood in a crimson colored ocean. Choi is convinced at this point that his blood contains tachyons, particles which move backwards. It would seem tachyons are not only connected to the theory of time travel or dimensional rifts but they also apply to Choi's physiology which would explain his loss of inches.
As Choi gathers himself, he comes under attack by a pod of monstrous tapeworms. Choi rides the tapeworms to avoid getting eaten then he realizes these tapeworms can fly. Choi is soaring through the air on this tapeworm until he finds a island in the sky. Choi jumps off the tapeworm and uses his bangstick to repel the creature back into the depths of the crimson ocean. Choi theorizes that his blood combined with the dimensional rift has created this unusual dimension and the tapeworms must have undergone some erratic evolution when they were plucked from Earth. On the island, Choi finds the people who were sucked into the rift. Panda explains to Choi that time moves rather fast as compared to Earth's reality. A second on Earth seems like a couple of months in this dimension.
By this time, Wilson has made himself leader of the islanders and Panda has started a relationship with Amanda, Choi's neighbor. Wilson tells the islanders to expel Choi from the island because he has injured the tapeworm and they will come back in numbers as a form of retaliation. Unfortunately, Wilson was right and the tapeworms began their assault. Choi uses his bangstick to keep the tapeworms at bay while Panda tries to convince Wilson into helping Choi. Wilson refuses to listen to reason and impales Panda with a shard of glass. Choi hears Amanda scream so he slows down the tapeworms' pursuit by causing a mountainside to come crumbling down thanks to his bangstick.
Choi finds Amanda crying over Panda's lifeless body and sees Wilson making a hasty exit. Choi catches up to Wilson and begins to beat him repeatedly. Unfortunately, a tapeworm comes crashing through but Choi dodges the tapeworm and watches as it devoured Wilson. Choi felt a deep sense of gratification that his friend had been avenged but then a temporal rift opens. The rift teleports the tapeworm first then it transports Choi to the same future that he went to when he tried to help Teddy Hyatt. Choi finds himself at the mercy of Lady Chronos. Choi also notices the tapeworm has evolved even further. It now possesses appendages which enable it to walk but Wilson's mind has become the force that drives the creature.
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...