Would make sense for me too.
The meteological spring begins on 1 March, unlike the astrological spring.
This year 21 March ( minus 10 days from 1582 ) then about mid-March.
By the way, from mythology. Pisces with the ribbon (cycle) of life and Aries looking after it. From the point of view of the ancient Egyptians.
An example of a chart where the year begins in March: You are not allowed to view links.
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Unfortunately, I don't understand it's meaning. I also don't understand the 13th month (last in the row).

The 13th 'month' is embolismus (annus), leap year
The whole thing is a computistic treatise, v. the description of the ms., the diagrams seem to be something about the leap year
(13-10-2022, 06:00 PM)Anton Wrote: You are not allowed to view links. Register or Login to view.Unfortunately, I don't understand it's meaning.
The four circles are quite readable, the one in the middle is more difficult.
ista figura deseruit anno bisextilem - this figure is used for a leap year
ista figura deseruit primo anno post bisextilem - this figure is used for the year after a leap year
ista figura deseruit secundo anno post bisextilem - this figure is used for the second year after a leap year
ista figura deseruit tertio anno post bisextilem - this figure is used for the third year after a leap year
Quote:I also don't understand the 13th month (last in the row). 
Embolis(m)us: (Medieval uncommon) insertion; (in literary work)
Circle in the middle
Item nondum quod in primis circumferentibus circulis figuram annos et in secundis habent hora et in tertiiis minuta habent
(13-10-2022, 06:50 PM)Helmut Winkler Wrote: You are not allowed to view links. Register or Login to view.The 13th 'month' is embolismus (annus), leap year
Are those the lunar months then?
While searching for "embolismus", I stumbled upon this reference which I find quite helpful: You are not allowed to view links.
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(13-10-2022, 07:25 PM)Helmut Winkler Wrote: You are not allowed to view links. Register or Login to view.Item nondum quod in primis circumferentibus circulis figuram annos et in secundis habent hora et in tertiiis minuta habent
I read "in externis circumferenciis iterum fig??rum aureus"...
Quote:In most medieval calendars, there are two other columns to the left of the names. Typically in the outermost column are Roman numerals running from one to nineteen. These numerals are known as the Golden Numbers, which help to find the date of Easter in any particular year, the Church’s most important feast. Easter is a so-called ‘moveable feast’, because its date is not fixed. Instead, it is dependent on the You are not allowed to view links. Register or Login to view.: Easter was celebrated on the Sunday following the first full moon after the vernal equinox (the spring date when day and night are the same length). The Golden Number tells you when the new moon will appear, and therefore, the date of the full moon fourteen days later.
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@ Nablator
what do you think of
in externis cirumferenciis circulum figurarum aurearum ...
the numbers 1 - 18 indicate the Golden number
(14-10-2022, 07:16 AM)Helmut Winkler Wrote: You are not allowed to view links. Register or Login to view.@ Nablator
what do you think of
in externis cirumferenciis circulum figurarum aurearum ...
There's something like an 'e' between fig- and -rum, maybe an 'a' in a too tight space and you're right. Your "circulum" seems to end in the same -rum abbreviation... not sure what it is then.
