Question

关于时刻的介词 half past eight 前不用加介词at吗，谢谢

Answer 1

这要看在句中所做的成分。
let's make it half past eight.它在句中做宾语补足语，不加at。
it's half past eight now.它作表语，不加at。
the boy begins to do homework at half past eight. 在句中做时间状语，要加at。

Answer 2

一般要加，但如果翻译时，是在八点半就要加，没说“在”时就不用加

Answer 3

根据情景决定，比如：
-What time is it? -It's half past eight (不加at);
-When will u be back? -At half past eight ,(需加介词)