Lyric discussion by cryingtimes 

Cover art for Tonight lyrics by Twenty One Pilots

"the young boy wants to move ahead and the old man sings rewind i wonder when in this timeline we'll break to the other side" ↳ tyler's noticed that people just wish to be at some other time in their life, where think things will be/were better. an "other side" we all wish for, but none of us ever seem to get there.

"maybe there's a span of time when we feel we're neither nor not wanting to go back again and not wanting to go forth" ↳ this point i believe is referring to the desire for death, which is not going backward nor forward in time.

"that point in life must be pretty dark and hopeless, terrifying and if you're asking me when that is" ↳ he's speaking from experience.

"it must be tonight" ↳ tyler has realized that point in his life is now.

"the old man sits all by himself and thinks of better years when he used to believe in stars and would dream away his fears" ↳ elaborating on the second line of the first verse, tyler may be suggesting that the old man doesn't necessarily have to feel this way.

"the young boy moves so fast he doesn't see the stars above and all his dreams are crushed by old men who didn't dream enough" ↳ elaborating on the first line of the first verse, tyler is explaining the problem with this cycle for all generations, perhaps speaking from his own experience.

"save me tonight" ↳ tyler ties his thoughts in with his relationship with his God, maybe asking if God can save him from this fate, or from suicide.

My Interpretation