一日的英文：
legal day (到午夜十二点为止)

参考例句：

October first is the National Day of China
十月一日是中国的国庆节

August the first is the Army Day of the Chinese People's Liberation Army.
八月一日是中国人民解放军的建军节。

Pancake Day (Shrove Tuesday,when pancakes are traditionally eaten)
薄饼日(忏悔节前一日,按传统吃薄饼).

I think that the rectification should go on till May 1 next year and that it should stop in the latter half of the year
我看整风搞到明年五月一日，下半年就不再搞了。

Chicks reared under natural light are frequently debeaked at 1 day of age or a few days after delivery to the brooder
在天然光线下饲养的小鸡，经常是在一日龄时或在进入育雏室后几天内断喙。

Rome was not Built in one day
罗马非一日建成

Rome was not Built in a (or one) day
罗马不是一日建成的

In the solar calendar, May the first is International Labor Day.
阳历五月一日是国际劳动节。

A three-sights-a-day tour
一日三游

to amerce one of a day's wage
罚一日的薪水

legal是什么意思：
adj. 法律的；合法的；法定的

Their legal challenge was unsuccessful.
他们的法律质疑未获成功。

To grant in a legal will;bequeath.
遗赠在遗嘱里言明送给；遗留给

legal deeds are rewarded By happiness.
善行会有幸福酬报。

legal guarding position
合法的防守位置

You must be in legal register age.
你必须达到法定的登记年龄。

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。