那是美好的一天用英文怎么说

"That was a beautiful day" 是表达那是美好的一天的常用英文表达。其中，"that" 指的是过去的某一天，"was" 是助动词，表示过去的动作，"a beautiful" 是形容词，表示美好的。

举例：

That was a beautiful day we spent at the beach. (那天我们在海滩度过的那天是美好的。)
I'm so glad we went for a hike, that was a beautiful day. (我很高兴我们去徒步旅行了，那天真是美好的。)
Yesterday was a beautiful day, the sun was shining and the birds were singing. (昨天是美好的一天，阳光明媚，鸟儿歌唱。)