1. those who are happy don't feel the time go by (put in a poetic, non-colloquial way)
2. schAst'ye = happiness
3. here: time = hours = 'chasY'

1. Te, kto schAstlivy, ne zamechAyut vrEmeni.
2. SchastLIViye lyUdi ne zamechAyut kak prokhOdit vrEmya.
3. SchastLIViye lyUdi ne zamechAyut kak leTIT vrEmya.

This quotation sounds poetic and in a way old-fashioned (speakers of modern Russian would never put it that way, because literally the quotation means: happy (people) don't observe hours). We would rather say something like: Te, kto schAstlivy, ne zamechAyut vrEmeni. It is also possible to say: SchastLIViye lyUdi ne zamechAyut kak prokhOdit vrEmya /ne zamechAyut kak leTIT vrEmya. By 'happy people' Griboedov meant those who are in love. This is clear from the context of his literary work 'GOre ot umA' - a very enjoyable and smart, thought provoking piece of writing. By the way, the Russian phrase 'vrEmya leTIT' is equivalent to the English 'time flies'.