when
1
什么时候, 何时
used when we want to ask at what time something happens
- Can you let me know when the package arrives?
你能告诉我包裹什么时候到吗？
- Can you tell me when the meeting begins?
你能告诉我会议什么时候开始吗？
- Do you remember when we met for the first time?
你还记得我们第一次见面的时候吗？
- I can't recall when we last spoke on the phone.
我不记得我们上次什么时候在电话里说过话了。
- When was the last time you visited your grandparents?
什么时候你上次去看望你的祖父母 ?
2
何时, 当
used to refer to a specific situation or time