I am trying to understand whether the Latin phrase below and its source text ought to be understood as solid evidence that the 11th Century author/compiler and subsequent users of the source text, as a matter of then accepted custom, placed January as the first month of the year. To clarify, if you were to ask a typical cleric of this time and this place to recite the names of the months from memory, would it be their mental reflex to begin with January or some other month? Or if a bishop were to invite me to visit him in the 'first month', in which month would he expect me to show up?
The phrase: Principium Jani sanctit tropicus Capricornus
The source: Un manuscrit chartrain du XIe siècle (A Chartrian Manuscript of the 11th Century) by Merlet and Clerval 1893.
See page 10 in the PDF version here: https://ia800503.us.archive.org/6/items/unmanuscritchart00merl/unmanuscritchart00merl.pdf
The exact context is that the phrase appears immediately below a miniaturize showing Janus warming his hands before a fire above the zodiacal sign of Capricornus. The broader context is that it is part of a series of "citations astronomiques qui se lisent dans notre manuscrit au-dessous de chaque miniature." (astronomical citations that read in our manuscript below each miniature). The complete "citation" for January, on page 24 of the PDF, reads:
Luna egyptiaca jan. I. IIII. V. VIII. XV.
Mensis jan. habet dies XXXI.
Epactas ɵ : Concurrentes Г.
Principium Jani sanctit tropicus Capricornus.
Jani prima dies et VII fine timetur.
Nox horas quindecim.
Dies habet decem.
Prima luna embolisimi.
Please understand that I have no Latin.
Richard J Legault