The Julian calendar was introduced by Julius Caesar (bust at right) in 45 B.C.E. Author David Duncan says the Julian calendar was born of Caesar`s tryst with Cleopatra.
Before the Julian calendar was introduced, priests in the Roman Empire exploited the calendar for political ends, inserting days and even months into the calendar to keep the politicians they favored in office. Tired of the chaos that this undependable system eventually gave rise to, Julius Caesar finally set out to put the long-abused calendar back on track.
It was in common use until the 1500s, when countries started changing to the Gregorian calendar (section the modern year). However, some countries (for example, Greece and Russia) used it into the 1900s, and the Orthodox church in Russia still uses it, as do some other Orthodox churches.
In the Julian calendar, the tropical year is approximated as 365 1/4 days = 365.25 days. This gives an error of 1 day in approximately 128 years.
The approximation 365 1/4 is achieved by having 1 leap year every 4 years