tomorrow is forever, and years pass in no time at all.
well, let me atomize the phrase a bit.
in no time att all means - right away, immediatelly (without a delay)
years pass - time goes by or runs out, ticks away very quickly
tomorrow is forever - suspecting, the poet meant it's never today, it is always tomorrow.
Overall, the meaing is quite clear to me. The author intended to say that time so quick as one cannot percieve. People should always look to future as the time flies and life is short. Thats what comes out to me.