Classic Rock, to me, is rock that does not derive its musical vocabulary from “Modern Rock”, which is any innovations to the musical vocabulary since and including Punk Rock.
Now, everything is on a continuum, so Alice in Chains, for instance, could be called nearly pure Classic Rock, but their production values and heavy guitars sound like their contemporary Grunge artists. Similarly, Coheed and Cambria, for all their progressive and epic sound, derive too much of their singing from punk, their pseudo-progressive sound from nu-metal rather than similarly-sounding prog-rock (although an argument could be made either way,) and on their first album, their short, high pitched hooks from emo, to be considered completely Classic Rock.
But both bands would be considered more Classic Rock than the Ramones, to me. I wouldn’t flinch if I heard A Favour House Atlantic on a classic rock station, whereas I would if I heard I Wanna Be Sedated.
I’d start with the end of the Beatles’ touring days. “I Want to Hold Your Hand” and the Beatlemania hits I think I’d call Golden Oldies. I’d start somewhere around the Revolver/Sgt Pepper era for classic rock.
I think I’d end it right around the release of the last good Rolling Stones album, Tatoo You in 1982.
I think Ludovic is on the right track: the key variable (other than time) is where one derives one’s musical vocabulary. Jimi Hendrix is in, because his music is part of the post-British Invasion flowering of rock n’ roll. Late '60s soul artists like Smokey and Aretha, not so much, so they’re out.
Too much of the folk-influenced singer-songwriter influence gets you kicked out, too, unless you’re Bob Dylan. No Joni Mitchell, no Cat Stevens, little if any Simon & Garfunkel.
all kidding aside though, definitely the late sixties, definitely the seventies and the first few years of the eighties. I know it when I hear it. does that count? I consider Stones and later Beatles to be classic rock, as well as Floyd, CSN, Creedence, The Who and Zepp. I also think that Yes, Genesis and Rush fit the bill. I can also see REO, Styx, BTO, Frampton, Boston, Kansas, Springsteen, Foreigner, Santana, T-Rex, Steppenwolf, Eddie Money, Billy Squier as classic rock. So what are the key elements? Guitars? AM radio? Beer? Beats me. I love the stuff, but it sure is hard to define.
What did you want them to do, an exegesis on the punk movement? They properly referenced punk in the context of the thread. They said that classic rock ends when punk begins, which is exactly “excluding” it, to use your own standard.
You can argue the dates of origin of punk as much as you can argue the dates of classic rock. But you can’t make a case for “punk was born in 1977”.