Personally, I think this topic is not only a math problem, but also a little Chinese.

This sighing brother actually hopes that today is Friday. I think we can reach an agreement on this.

There are two unknown values in the whole question * *.

The first one is "what day is the real today", which is the answer to the question. Let this unknown week be a day.

The second is that the difference between "real today" and "I hope today is Friday, that is, hypothetical today" is set to B.

Look at the second sentence in the title, "So today is Friday", from which the following equation can be listed:

"hypothetical today" =a+b

Suppose today is Friday, then

5=a+b

Let's look at the first sentence of the title.

If only yesterday were tomorrow,

There are two possible meanings of this sentence:

First: "real yesterday" = "hypothetical tomorrow"

a- 1=a+b+ 1

a- 1-a- 1=b

-2=b

because

5=a+b

a=5-b

a=5-(-2)

a=7

So today is really Sunday.

When Sunday is almost over, how much we wish yesterday (Saturday) was tomorrow, so today is Friday.

We can have another weekend.

Second: "hypothetical yesterday" = "real tomorrow"

a+b- 1=a+ 1

b=a+ 1-a+ 1

b=2

because

5=a+b

a=5-b

a=5-2

a=3

So the real today may be Wednesday.

When every week is just after Wednesday, how much we wish yesterday was tomorrow (Thursday), then today is Friday.

Tomorrow is the weekend.

So the answer to this question is Wednesday or Sunday.