The Gregorian calendar was adopted by much of Catholic Europe in 1582, as directed by Pope Gregory XIII in the papal bull Inter gravissimas, which was published in February of that year.

What is our calendar based on?

Gregorian calendar The Gregorian calendar is the calendar used in most of the world .Beginning of the year.CountryStart numbered year on 1 JanuaryAdoption of Gregorian calendarPapal States15831582Holy Roman Empire (Catholic states)15441583Spain, Poland, Portugal15561582Holy Roman Empire (Protestant states)1559170012 more rows

Who invented calendar?

In 45 B.C., Julius Caesar ordered a calendar consisting of twelve months based on a solar year. This calendar employed a cycle of three years of 365 days, followed by a year of 366 days (leap year). When first implemented, the Julian Calendar also moved the beginning of the year from March 1 to January 1.