[details=“English Translation”]He is off today.[/details] I take it this is about not being in for work rather than behaving strangely.
English Translation
He is free today.
agreed, clearer as ‘he is free/available today’
English Translation
He is off today.
I don’t agree it’s clearer, someone is off is the first thing that comes to my mind and if it were free today, it would be too easy and it wouldn’t be the most efficient way of learning the word.