"should have (done)" always contain the meaning of regret?

If I want to make the following sentence to the past tense, would it be fine to write like the second sentence?

- He should submit the paper to the professor by next Thursday.

- He should have submitted the paper to the professor before last Thursday.
(No feeling of regret or blaming him, but I am sure he submitted the paper...)


Thank you in advance!

See a translation

No, "should have (done)" does not always mean "regret".

It is tricky when written out, though. How you used it *can* work, but that sentence also *could* convey regret. If the sentence were spoken aloud, we would know if it was regret or supposition based on the speaker's tone of voice. Written out, without hearing a voice, it is difficult to know if it is regret or supposition.

There are two ways around this. One is simply to re-write the sentence in a way that regret cannot be a possible meaning anymore. That would be something like "I think he submitted the paper to the professor...", or as you wrote it, "I am sure he submitted it..."

The second is including context. Look at these examples--blame first, then supposition.

Blame
A: "I heard he got a bad grade on his paper."
B: "He should have submitted it before Thursday."
In this example, B implies the bad grade was because the paper was late.

Supposition
A: "Do you know if he turned in his paper?"
B: "He should have submitted it before Thursday."
Here, B implies that they don't know if "he" submitted it, but there's no reason they can think of that "he" didn't get it submitted on time.

So, depending on context, the exact same sentence can or can not imply blame!