Hello,
Could there be a tooltip with a short description of the calendar/era? like the one shown when hovering over catalogues.
For the Hijri calendar, it could be something like this:
“Islamic calendar consisting of twelve lunar months and 354 or 355 days. Hijri year 1 began on 15 or 16 July AD 622.”
For the Actian era:
“Ancient Roman era of the Julian calendar, set in reference to the battle of Actium. Actian year 1 probably began at the end of August 31 BC. The Julian calendar had years with 12 months and 365 days and leap years with 366 days.”
For the Galba era:
“Ancient Roman regnal era of Emperor Galba based on the Julian calendar. Year 1 probably corresponded to 8 June - August AD 68 and year 2 to August AD 68 - 15 January AD 69. The Julian calendar had years with 12 months and 365 days and leap years with 366 days.”