If you’re one of those TDL.DR sort of people, I expect you missed the bit in my last post about orthography on the Picard astrolabe (as Don of Talahassee tells it), and D.A. King’s commentary on the same astrolabe – where he cautions against dating it to the early fourteenth century only by its placing the equinox at about March
10th 12th. (thanks).
Pisces has been the equinox constellation since about the year +1 AD or so.
When Julius Caesar established his calendar in 45 BC he set 25 March as the spring equinox. Because a Julian year (365.25 days) is slightly longer than the tropical year the calendar drifted with respect to the equinox, such that the equinox was occurring on about 21 March in AD 300 and by AD 1500 it had reached 11 March.
picture.. from Opicinus (notice the pointy little nose)?
IMO – naturally.
(less than a 150 words)