当天的英文：
that day
the same day

参考例句：

The special of the day is a roast of pork .
当天的风味菜是烤猪肉。

At close of play,ie at the end of the day's play in a cricket match
当天在板球比赛结束的时候.

I will be thinking of you on Valentine's Day.
情人节当天我将思念你。

Whilst reading the morning newspaper (ink-CPI, paper--processed using chemicals from CPI).
一边读着当天的晨报（墨水---CPI，纸--用CPI生产的化学品加工）。

Rehearse the events of the day
列举当天发生的事情

Each has his quota of work for the day.
每个人都有一份当天的工作。

The door of the carriage was thrown open, to let out the very blossom of the day
车门打开，当天的中心人物露面了。

She writes up her diary every evening.
她每天晚上记当天的日记。

He adverted briefly to the news of the day.
他简短地谈了当天的消息。

He hopped up to Boston for the day
他当天乘飞机去波士顿。

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。