on August 1st 是人们最常用的表达方式。
两个用法皆正确，但具体如何使用还要看当地的语言习惯。请注意 "August 1st" 通常会被写作"August 1"，但读作"August first"。
Come and see us at the lake on August 1st. It will be a great time for all!
Are you doing anything on August 1st? If not, come and have a party in our yard.
On August 1st, the company will make a big announcement about pricing.
Anything happening on August 1st this year?
What will she be doing on the evening of August 1st?
Where were you on the night of August 1st, Mr. Campbell?
I don't know what this issue with August 1st is all about.
Is the party on August 1st or August 2nd?
You'll look after the tree until the 1st of August.
We won't see each other again until the 1st of August.
I expect you'll come to Warsaw, like every year, on the 1st of August to visit the boys' grave.
It may not be on the 1st of August, it may be January 8th.
Is it usually this hot around here on the 1st of August?
What is she going to do on the 1st of August?
The 1st of August is auspiciously austere and yet audacious.