As I understand it, July 2010 was literally the first commit for Swift in any form (https://techcrunch.com/2014/06/04/apples-new-programming-lan...), as a personal project for Chris Lattner. I think the complete history is on Github now.

Of course, age only tells you so much about the amount of work put into the project, and Rust in particular took a huge amount of conceptual work to get its current model of ownership.