In 46 BC Julius Caesar the Roman Emperor consulted a group of Egyptian astronomers and it paid off with the timetable which most of the world is governed by more than a millennium. Thus he was born leap year, but if there were, currently be in July 2017
This has to do with the solar year. Egyptian astronomers then could detect something that the Romans: one calendar year is delayed a bit compared with the solar year, which means that a year actually is composed of 365 exact days, but 365.2422 days. To not go crazy Caesar and his team determined that the best way to measure an additional year was added to the calendar every four years day.
The problem is that this also results in an accurate measurement. The year is not composed of 325.25 days but 365.2422 days, which means that you can not join four quarters for four years to form a new day. There is a difference of 11 minutes and 40 seconds each year, which involved adding an extra day to the calendar every 125 years.
The Roman calendar lasted well until the mid-sixteenth century, a time when Pope Gregory XIII of the Catholic Church decided to change it again for the purpose it was easier to determine exactly when was the lark, and thus was born the Gregorian calendar today day use in most of the world.
Source: Gizmodo