我们要珍惜时间。

We should value our time highly.

Beside a river Confucious once said:

子在川上曰；

The passage of time is just like the flow of water, which goes on day and night.

逝者如斯夫,不舍昼夜。

Time flies like an arrow, and time lost never returns.

光阴似箭，一去不返。

Time flies and another year go by. 

时光飞逝,转眼又是一年。

Time flies and life is short.

光阴似箭而人生短暂。

Time flies when you are online.

上网的时候时间过得飞快。

Time flies when you're having fun.

开心的时候会觉得时间飞快。

Art is long, and time is fleeting. 

时光飞逝, 学艺无穷。

Time flies. You should work harder.

时光飞逝，你应该要更认真工作。

Time flies by, and a world of changes has occurred.

光阴荏苒，世事沧桑。

We should learn how to cherish time and use it efficiently.

我们应该学习如何珍惜时间且并有效率的利用它。

Those who go before time can best value their time.

走在时间前面的人最会珍惜时间。

Improve your time and your time will improve you

你珍惜时间,时间才会珍惜你。