In English, "Is it Tuesday already?" and "Is it Tuesday yet?" are not the same.
"Is it Tuesday already?" implies that it IS Tuesday, but you are surprised (perhaps because you thought it was only Monday).
"Is it Tuesday yet?" means that you are not sure what day it is today and are asking (perhaps because you have something you have to do on Tuesday, and need to know whether it is time to do it).
Why does "It is Tuesday" work? Only "Is it already Tuesday" and "Is it Tuesday yet?" are accepted.
Because it's a question, the subject and verb are in reverse order in English.
Un mnemonico that I used, I first wrote chà instead of già, because the sound is the same, then I googled gia and I encountered : Gemological Institute of America. E vedere qui ! I have my mnemonic !