Fun to think about all the alien contact with Earth prior to First Contact. If you count cases where humans interacted with aliens without knowing they were aliens, you get the Roman gods.
...Probably not - humans aren't that stupid. It's when humans interact with aliens like Apollo's folks, then die, and their great-great-great-grandchildren
forget, that a nicely quantifiable alien visitation turns into a murky legend about the Greco-Roman sort of gods.
If the human knowing the person in front of them is an alien is required, you can at least go as far back as Mark Twain, I can't remember if there are other time travel episodes where they go back further and the humans learn for a fact the person is an alien.
Q interfered often enough with Earth history. Can we really attribute him with the sort of tact that would keep his divine, alien powers unnoticed? Thaddeus Riker probably had at least an inkling he had been visited by a nonhuman.
No, I can't recall a definite reference to a revealed alien visitation to Earth from an earlier era, either. But it would be rather unthinkable that none took place.
First contact is really the initiating event that led to the general public becoming aware of aliens.
So first contact with Apollo's party probably meets the criteria. It's just that later generations of this general public forgot.
So first contact with Cardassians would be the incident that led to humans and Cardassians both learning the other existed.
But the definition of "general public" may not be all that broader in the Federation than it was back on Peloponnesos. Those (tens of?) thousands of years go, messages traveled slowly and became corrupted because of technological limitations. From the 22nd century Federation onwards (and indeed here down on Earth from the 19th century on), they would face different hurdles, applied to enforce the need to know.
Depending on how the high and mighty decide on that need, the open database may contain everything on Tellarites, only a select few facts on Vulcans, and nothing on Cardassians - but there also exists the secret database, available at Cadet Tilly's keypress unless Commander Saru decides against it.
That database supposedly contains all the dirt on Vulcans and everything required for meeting the criteria of proper first contact with Cardassians.
If the governments know, the ignorance of the rank and file shouldn't IMHO be counted against first contact having happened.
And yes, by those standards, Columbus would also be the one who made 'first contact' with North America for Europe.
But so would Lucky Leif. His message did propagate to
his general public, with the full force of propaganda to boot.
The word commemorate implies that you are honoring the thing, so it's probably not the right word to talk about Columbus.
Why would it imply that? The commonly used word for holocaust remembrance is "commemorate", too. Indeed, at a quick glance, most "Days of Remembrance" are defined using that word on their online publicity material.
Timo Saloniemi