Months names are all one off?

[RobGea]

Seems to me this whole medieval astrology thing was hella complex.

Found this Masters thesis from 2013 by Irene Meekes - van Toer "Practical Advice in a Late-Fifteenth-Century Astrological Calendar Manuscript. Amsterdam UB MS XXIII A 8."
about a manuscipt in the Amsterdam University Special Collections Library.
The codex Amsterdam UB MS XXIII A 8 basically consists of a twelve-month calendar dating from about the last quarter of the fifteenth century.(1475-1500 AD)

The thesis itself is choc-a-bloc with medieval goodness and imho worth a read just for that.

I cannot find how the Zodiac signs were specifically dated but she does say this.

Tradition dictates that the transition from one sign to another take place in the middle of each month.
This is reflected in our calendar,
where we find the Latin formulation "Sol in [aquario etc.]"
written in the margin of each calendar month.
The rules for each sign are thus valid for a month at a time.

Thesis is in English. Link to its description (Msc link on that page)   -> You are not allowed to view links. Register or Login to view.