英语中什么情况下时间前不加介词

Question

如题，可以用过去时的例子说明。
比如 I bought a car last year ago
last year ago前为什么没有像at之类的介词

Answer 1

在平时的学习中,我们注意到一般的时间状语前都有介词in/on/at或for 等,而实际上在英语中,有不少表示时间的状语前是不加介词的.
1.在 today, tomorrow, yesterday, the day before yesterday, 等表示时间概念的名词前一般不用介词. 例如:

1) What are you going to do tomorrow?

你们明天打算干什么?

2) We have had six lessons today.

我们今天上了六节课.

3) We had a good time the day before yesterday.

我们前天玩的很开心.

2.由this, that ,these, those 等用于表示时间概念的名词前,

前面往往不加介词.例如:

1) That morning he got up very early.

那天早上他起得很早.

2) What are you busy with these days?

这几天你在忙些什么?

3) We will have a big gathering this coming Saturday.

下星期六我们将进行一次大聚会.

3.由next, last, the next, the last 等用于表示时间概念的名词前时,前面不用介词修饰.例如：

1) We planted many trees last spring.

去年春天我们栽了许多树.

2) She said she would pay a trip to Suzhou the next month.

他说他下个月将去苏州.

3) The very next time I saw her, she was working in London.

在那次之后我又见到他时,他正在伦敦工作.

4.在each, any, every, some, all 等用于表示时间概念的名词前,一般不用介词来修饰. 例如:

1) The buses go every 10 minutes.

汽车每隔10分钟一辆.

2) Jack coughed all night.

杰克咳了一整夜.

3) We have to get up very early every day.

每天我们都必须早早起来.

那个得ON 因为是具体的某天上午或下午前

Answer 2

tomorrow,yesterday,today等前不加介词，the next/last...也不加.等

Answer 3

1今天是星期天 It's Sunday today.
2现在是下午六点 It's six pm now.