I remember begging my folks to let me stay up late when I was a child to watch "Day of the Dove." This was first run. I distinctly remember the promo for it. Which means my parents were watching "Specter of the Gun" that night--so that would have been October 1968. And I'm sure that I got to stay up to see DaotD,
But like so many others here I got hooked in my teens in the 70s, in late night syndication. WPIX, channel 11 NYC. I remember the first time I saw an episode that wasn't butchered in syndication (some time in the late 80s I think)--that was "Mirror, Mirror." Do you know that for years I had never seen the scene of the Mirror Kirk, Scott, McCoy, and Uhura, you know, being savages on the main universe's Enterprise? But I guess that was so with most of us 70s types.