AKA Safely Walk Near Manholes Day
Cover Day could have many possible meanings, and it does.
You can cover something like a bed with a blanket.
You can cover something like a pot, a pan, or a bowl with a lid.
You can cover yourself with something like clothes, including coveralls.
You can write a cover letter. Philatelists call collectible envelopes covers.
You can cover a song that someone else did before you. Whether you make it better or worse doesn't matter.
They used to call song covers remakes. I'm not sure exactly when the terminology changed, but it must have been during the 80s or 90s.
Do you remember remakes? If not, that would help me pin down the year of the changeover.
The one type of cover that you might want to avoid today is the cover up. People have gotten into deep doo-doo by participating in a cover up. You don't want to be like said people.
Keep your covers clean. You'll thank me for that advice.