make it half past six.这个句子中应不应该加at,为什么?

Let's make it half past six.为什么half past six前面不加at Let's make it half past six . 仁爱版八年级英语教材中有个句子“Let's make it half past six”,怎么不用介词at呀? at half past six let's make it half past eight为什么具体时间前不加介词at Let's make it half past seven中为什么时间前不用at Let's make it half past six.make在这儿当什么讲? At half past six是何意思? come at half past six意思,急, It's half past six.啥意思? It's half past six(what) 英语翻译when shall we meet?let＇s make it half past six