Kalends

Pliny tells us that cloud rose into the sky on the ninth day before the Kalends of September (which would be 24 August, as we count it).

Instead, they counted back from three fixed points of the month: the Nones (5th or 7th, depending on the length of the month), the Ides (13th or 15th), and the Kalends (1st of the following month).

In the Roman system, each month had three fixed points known as Kalends (Kal), the Nons and the Ides.

It renamed the first month Dios as Kaisar, and arranged the months such that each month started on the ninth day before the kalends of the corresponding Roman month; thus the year began on 23 September, Augustus' birthday.

Oct. Every month begins on the ninth day before the kalends.

The day preceding the Kalends, Nones, or Ides was Pridie, e.g., Prid.

The new leap day was dated as ante diem bis sextum Kalendas Martias ('the sixth doubled before the Kalends of March'), usually abbreviated as a.d. bis VI Kal.