It probably began about the 10th of March, at that period about the time of the vernal equinox, according to the Julian calendar.
The inventor of the calendar ordered that it should be known as the "Julian calendar," and it is so called, even unto this day.
According to the Julian calendar, which was then in use, July 25 fell seven or eight days later than now.
The Julian year is a year of the Julian calendar, in which there is leap year every fourth year.
The whole question is more or less complicated by the fact that the Julian calendar was in use.