Chinese aspect-markers like 了、过 and 着 show the temporal relation an event has to the time-period you are talking about. However, unlike tense-marking on English verbs, where we obligatorily mark each verb with the appropriate tense (-ed, -t, -en, -ing etc.), Chinese has a tendency to ONLY put aspect-markers after the MAIN verb of the sentence – regardless of their ‘tense’.
中文秘诀 | The Secret of Chinese 