And February 30th is a thing
Was there a July 19, 3110 BC? Yes.
Did anyone actually call it that at the time? Almost certainly, no, as even if they could see into the future, there was no language at the time where the words “before Christ” existed.
Was there a day that we would consider to be July 19, 3110 BC? Yes, but of course, there are multiple ways to calculate that. Did February 29, 100 BC exist? Remember that February 29, 1900 existed in the Julian calendar, but not the Gregorian one, and your guess is as good as mine as to how the World calendar handles leap years (although “leap day” is the last day of June).
Fun fact of the day: in Oracle, if you subtract 1 day from 1/1/1 CE, you get 12/31/1 BCE, but if you list their “day numbers”, they are 367 apart, as if “year zero” had 366 days in it.
Will there be a July 19, 3110 AD? There is no way to answer that for sure, but as my Magic 8-Ball says, “All signs point to yes.” The only way it is “no” is if, somehow, the universe collapses in on itself before then.
There’s also the whole BC/AD versus BCE/CE thing, but that’s another matter.
There’s a difference between a system used to label and describe something and the thing itself.
“July 19, 3110 BC” is a label that identifies a period of time in a commonly-used measurement system. That period of time existed no matter what anyone calls it, or even whether anyone called it anything. There’s no reason that people today can’t or shouldn’t use the modern system to identify a period of time that happened long before that system was invented. It’s like using meters instead of cubits when talking about the height of King Solomon.
The Chicxulub crater was created by an asteroid hitting the earth. This event led to a mass extinction. When did it happen? Does it make sense to give an approximate date for this event in years BC (or some other measurement) when there were no people around when it happened?
Great! They are taking over our payroll system. According to my paystub I’ll work 4937 hours in a week and get $6.29 for it.
Yes by counting how many perihelions there have been between now and then.
That’s my point. You can apply any standard you want to identify and measure past events, even if no one at that time used that standard. Counting perihelions is a reasonable standard, given that it’s based on something that’s more-or-less constant over time, but no dinosaur (or anything else living at that time) knew what a perihelion is.
That and a couple of other calendrical oddities are mentioned here. I personally find December 32, 1980, rather heartwarming.