That is a question I saw in Chinese，I translate it into English here。
Today is Sunday to this question.
On Sunday the speaker says:" if yesterday were tomorrow，then today would be Friday." So yesterday was Saturday, and the speaker means if tomorrow were yesterday and yesterday was Saturday , so if tomorrow were Saturday, then today would be Friday, matching your question.
If on Wednesday the speaker says if tomorrow were yesterday,and yesterday was Tuesday, so if tomorrow was Tuesday, then today would be Monday, not Friday!
--It's my opinion.
If I were to be tomorrow what I thought I was yesterday, what might I be if I weren't the same me as I thought I was or if tomorrow turns out to be another day altogether?
How to obfuscate! hahaha
It is a nonsense question - you may answer as you please . How about 'well naturally it is 'Qing Ming Jie' or 'it is PI day'
The key is that whether "yesterday was tomorrow" is equal to "tomorrow was yesterday".