Thanks to all of you for helping me out here! I discussed this with a fellow English teacher today, what the kids should reply to the question "What day is today?" - makes me feel good I was quite right with a) 
https://twitter.com/The_Solista/status/1219247440836034560 …
Dear native English speakers out there... pls help me solve an argument!
Do you say:
a) Today is Monday.
or
b) Today it's Monday. pic.twitter.com/CqJEFqKWJU
Do you say:
a) Today is Monday.
or
b) Today it's Monday. pic.twitter.com/CqJEFqKWJU