The Republican presidential candidate notified Beth Myers, who was running his VP search, and called up Ryan that day to set up a meeting.
It's unclear when exactly Romney made the formal offer to Ryan.
The campaign did not confirm the selection publicly until Saturday morning.
Romney is formally announcing his decision at a campaign stop in Virginia.
Carl Cameron currently serves as Fox News Channel's (FNC) Washington-based chief political correspondent. He joined FNC in 1996 as a correspondent.