
Both tenses refer to the past, but they differ based on whether a specific time is mentioned and whether there is a connection to the present:
- Past Simple: The action ended at a definite time in the past and has no relevance to the present.
- Present Perfect: No specific time is mentioned; it emphasizes the impact on or experience related to the present.
我I 看saw 他him 昨天yesterday.
I saw him yesterday. (Definite time → Past Simple)
我I (完成时)have 看seen 那部that 电影film.
I have seen that movie. (Experience, no specific time mentioned → Present Perfect)
Note: Once definite past time markers such as yesterday, last week, in 2019, or ago appear, use the Past Simple, not the Present Perfect.