If civilization continues to the year 9999, is the idea to go to year 10.000, or...?
It seems like it'd get increasingly impractical as the years go on to hundreds of thousands and millions of years to write them out that way, but then...I guess technically one may already do this with the preceding years, so future's fair game for it?
Astronomers already use Julian Dates for various reasons. Right now it's 2460261.2834606, it'll be later by the time you read this. Julian dates/times are fractional days starting from January 1st, 4713 B.C. = 0. Just keep counting up from there.
So I just read through the same wiki and there is absolutely no explanation of why they start at 4713 BC. It's just bizarrely stated as fact with no explanation.
It would be like if invented a card game called Percluey where you had to count to 44 and Yell "Percluey" to win the game. And 8s are also called perclueys and worth -3. Then when you ask why it's 44 you just say "because that's Percluey" and then when they ask you what the heck is a "Percluey" you just shrug and sip on your spritzer.
I don’t know if you read the right wiki, but in the history section the first paragraph is:
The Julian day number is based on the Julian Period proposed by Joseph Scaliger, a classical scholar, in 1583 (one year after the Gregorian calendar reform) as it is the product of three calendar cycles used with the Julian calendar:
Its epoch occurs when all three cycles (if they are continued backward far enough) were in their first year together. Years of the Julian Period are counted from this year, 4713 BC, as year 1, which was chosen to be before any historical record.[28]
It was either that, or earlier, or in the future. That’s the only year that kinda makes sense (solar = lunar = induction = 0). It looks odd but once you know you know, you know?