slip away

(verb) leave furtively and stealthily. Synonyms: slip away, steal away, sneak away, sneak off, sneak out. Example: "The lecture was boring and many students slipped out when the instructor turned towards the blackboard."

(verb) pass by. Synonyms: elapse, lapse, pass, slip by, glide by, slip away, go by, slide by, go along. Example: "Three years elapsed."