When Acne-Plagued Teenagers Are Shunned From Hootenannies And Other Such Wholesome, Non-Pimply Activities

I'd place the date on this ad as being between 1961 and 1964.

Even network television got in on the Hootenanny trend:

My favorite of the Hootenanny groups was The Journeymen, which was Dick Weissman, Scott McKenzie, and John Phillips. 

This was filmed in the fall of 1963.