My first child was born on March 15 last year. This spiked my interest in the famous or rather infamous "Ides of March" and the Jullian Calendar. I have been noticing that different sources on the internet have it spelled different ways. I have seen IDES, EIDES, EIDUS or EIDVS. And March is MARTIVS.
My question is which is correct and what recommendation might you have of a good source on the Ancient Roman Jullian Calendar that I can reference?
If you look at these photos of original Roman fasti, you can see the original spelling "EIDVS" (abbreviated as "EID").
The vowel we write as "U" in modern English was written as "V" in ancient Latin. Gaius Julius Caesar's name was written as CAIVS IVLIVS CAESAR. Therefore, "EIDUS" is a modern representation of the original version, to show that there's a vowel in that second syllable rather than the "v" consonant we modern English readers would otherwise assume.
There are a lot of Anglicised versions of Roman words and names. To take a well-known example, Mark Antony was actually Marcus Antonius (MARCVS ANTONIVS). Octavian was actually Gaius Julius Caesar Octavianus. Similarly, "IDES" is the English version of EIDVS.
The original month was named after the Roman God of war: Martius (or MARTIVS). March is, again, the modern English version of that name.