I was going to write command
tmux detach but I accidentally pressed some other key/ key combinations and saw a big clock on the whole terminal. There was just time printed and nothing else.
I don't know whether it appeared because of a package I installed unknowingly or because of a native Linux/centos package.
The most relatable thing that I could say I found was is the image present in this answer.
The text font was very much similar to the font present in the above-mentioned image.