Gregorian calendar

基本解释

The Gregorian calendar was not widely adopted across the world until much later.
格里高利历法（公历）直到很久以后都未被世界采用。
With the reform of the calendar under Charles IX, the Gregorian Calendar was introduced, and New Year's Day was moved to January 1.
后来随着查理九世对日历的改革，格里高里历被引进，新年也随之移到了1月1日。
ORIGIN: the exact origin of April Fool's Day isn't known, but many think it began in France around 1582 with the introduction of the Gregorian Calendar, which is the most widely used calendar today.
起源：四月愚人节的确切起源已不可考，不过很多人认为这个节日是起源于1582年前后的法国，在公历被引进之后——公历就是我们到今天还在使用的历法。

We controlled for other well-known fixed calendar (we call them Gregorian anomalies), notably,day of the week effect, like Monday,January effect, Halloween effect, and none of those factors explained results.

The Gregorian calendar is used today in the large majority of countries.
UNESCO: International Women’s Day: why the 8 of March?
Clavius started his career by taking on the reform of the Gregorian calendar, a project partly inspired by Copernicus and his book.
FORBES: A Long Forgotten Father of the Scientific Revolution
Britain adopted the Gregorian calendar only in 1752.
ECONOMIST: Late for the date

the revision of the Julian calendar introduced in 1582 by Pope Gregory XIII and still in force, whereby the ordinary year is made to consist of 365 days and a leap year occurs in every year whose number is divisible by four, except those centenary years, such as 1900, whose numbers are not divisible by 400