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Just a guess, becasue this is perhaps my favorite lyric of all time. If one inserts a few words "like a smoke ring <ON A> day when the wind blows, it makes perfect sense given the context of the song. The words are omitted to keep the meter of the verse. This song was Neils kiss-off to Buffalo Springfield, and a stunning lyric IMHO. ~Dave in Nashville~
I think you'll find it's a song written by Neil Young... who by the way is an amazing artist, lyrical genius & not afraid of saying what needs to be said... check out Ohio, Cortez The Killer & Let's Impeach The President!

The term 'smoke ring day' does as it suggest involve smoke; of the mind altering variety...
It's a turn of phrase to suggest intoxication, a 'Hazy Jane' kind of day... (listen to The Thoughts Of Maryjane by Nick Drake and you'll get the idea)

Hope that clears it up a little for you...
Students: We have free audio pronunciation exercises.
Thank you very much. now it made sense.
i'm brazilian portuguese speaker.
i knew this amazing song from one my favorite brazilian bands

watch if you want:

Neil Young's "On the way Home" used to go:

"I went insane like a smoke ring DANGLING when the wind blows."

Now it's a smoke ring DAY. (Not days)

What is a smoke ring DAY?