随便哪一天的英文：
any day

day是什么意思：
n. 一天；白昼，白天；工作日；时代，时期

Things go on day by day.
事情逐日进行着。

Day by day the situation is improving.
情况在一天天地好转。

Like this, day after day.
就这样，日复一日。

It was a fateful day.
那是个不祥的日子。

Meantime, from day to day they endure.
同时，一天天他们捱了下去。