Since Target's original announcement that up to 40 million customer credit and debit card accounts had been hacked, critics have questioned why it took the retailer four days to come clean on the data breach.
Now, for the first time since the security breach was announced on Dec. 19, Target Chairman and CEO Gregg Steinhafel is speaking out. While four days may seem like a long time for consumers to learn their sensitive account information was at risk, Steinhafel argued that it was lightning speed from Target's perspective.
He laid out what happened from the moment he knew there was a problem.
(Read more: 'I'm still shaken' by Target data breach, says CEO)
"Sunday (Dec. 15) was really day one. That was the day we confirmed we had an issue and so our number one priority was ... making our environment safe and secure. By six o'clock at night, our environment was safe and secure. We eliminated the malware in the access point, we were very confident that coming into Monday guests could come to Target and shop with confidence and no risk," Steinhafel said.
"Day two was really about initiating the investigation work and the forensic work ... that has been ongoing. Day three was about preparation. We wanted to make sure our stores and our call centers could be as prepared as possible, and day four was about notification," he added. (The full interview will air on CNBC's Squawk Box Monday.)