August 17, 1992. 

36 Minutes.  The entire address is worth a watch.  But if you don't have time....just watch from the 12-17 minute marks.  And then the final 2 minutes.  It's pretty extraordinary.  

Reagan was 81 (same age as Biden today, coincidentally).  To the best of my knowledge, this was his final public speech.    

www.youtube.com/watch