Well the Romans had two ways of keeping the year. One was to state the two consuls that were elected that year and in 59 BC that was Gaius Julius Caesar and Marcus Calpurnius Bibulus. So the Romans would state 59 BC as the year of Caesar and Bibulus. They also jokingly called it the year of Julius and Caesar becuase of the fact that Bibulus hated Caesar and so he withdrew to his home and refused to work with Caesar. This made caesar do both consul's work by himself.
The other way that Romans told time was in reference to when rome was founded so since Rome was founded in 753 BC, 59 BC would be the 694th year of the City
Hi, hopefully someone can give you the exact number, but meanwhile you may be interested in this section of the FAQ