3月12日用英语表达是：March 12th；

March：n. 三月。

例句：

In March and April, the weather is much less predictable.

三、四月份的天气非常不好预测。

All countries march as one nation under the banner of friendship.

所有国家在友谊的旗帜下团结一致，共同前进。

The people marched en masse.

人们齐步前进。

March is one of the peak periods for our business.

三月是我们公司业务最繁忙的时期之一。

Time marches on and we still have not made a decision.

时间过得飞快，而我们却还没有拿定主意。

The country has been on a war footing since March.

自三月份起这个国家就准备要打仗。