Months names are all one off?

[nablator]

The books that @nablator and I found have the same text as the Prague MS You are not allowed to view links. Register or Login to view. "Textus astronomici (1400-1450)", but that is not the same.

The claim of @BessAgritianin remains to be confirmed.

The part that I quoted, starting with "Aries est animal, quod in parte anteriori viget, posteriori vero debile est" is pretty much the same in Sacrobosco's book and BessAgritianin's manuscript page. Before that there is the different introduction translated by Marco "This sign (Aries) is fiery and it spans the end of March and half of April" and a few words (that I couldn't figure out entirely) about it being attributed to April as it ends in April: not much of an explanation but that's all there is.