Question

we are having a party at eight o'clock in the afternoon on New Year's Day.这句话对吗？

Answer 1

不对。are 要改成were。因为这是过去进行时。
另外，on改成of更好。

Answer 2

(如果表示“计划中即将举办”，可改为：

We （are going to have） a party at eight o'clock in the evening (晚八点已经不是afternoon 了）on the New Year's Day.

如果说新年那晚8点我们正在开晚会。== 应该是过去进行时，或将来进行时

We were having a party at eight o'clock in the evening the last New Year's Day. (上个新年）

We will be having a party at eight o'clock in the evening on the coming New Year's Day.(即将到来的新年）

Answer 3

如果师表不久的将来，用are having没错，倒是后面的时间，建议改为; at eight p.m on New Year's Day.就表示出来了，既简练又符合行文习惯。

Answer 4

最好用：be going to 的句型。不然，你这句子会让人误解为 现在进行时。
we are going to have/throw a party ……

Answer 5

on+具体日期，不用改成of
你的句子对
相信我