It went into operation January 1st, 45.

He employed Sosigenes, an Alexandrian astronomer, to superintend the reform.
While Sosigenes was at work on the calendar, Caesar purified the Senate.
Many who were guilty of extortion and corruption were expelled, and the vacancies filled with persons of merit.
Meanwhile matters in Spain were not satisfactory.

After the battle of Pharsalia, Cassius Longinus, Trebonius, and Marcus Aemilius Lepidus had been sent to govern the province.

They could not agree.

The soldiers became mutinous.