Google Doodle celebrates the 434th anniversary of the Gregorian calendar, which was introduced on Oct. 4, 1582, by Pope Gregory XIII.
The new calendar, introduced during the Renaissance, replaced the Roman Calendar that Julius Caesar had reformed in around 46 B.C. Before Caesar realigned the calendar, a Roman year had been 10 days shorter than a current year, and divided into lunar months. In order to keep the year in tune with the seasons, an extra month would be tacked on occasionally.
Caesar noticed that Egyptians used a calendar based on the sun rather than the moon. So, in consultation with the Alexandrian astronomer Sosigenes, he decided to create his own new system, hoping to solve the problem of the drifting seasons.

Each solar year in Caesar’s calendar became 365 days and six hours long, and the shortest month would get an extra day every four years to account for the annual accumulation of a quarter of a day. He made that first year 445 days long, so that the transition between the old Roman calendar and the new one would work.


However, Caesar’s estimation was http://chinedusamuel..com.ng/2016/10/google-doodle-marks-434-years-gregorian-calendar.html