Here are some examples with the putative should. What is the factor which indicates the time reference expressed by the putative should in the examples? Being a foreigner to English I find it hard to clearly see the time reference.
1 I'm surprised that he should say it to you. (Has he already said it or is it going to happen in the future?)
2 It's a pity that they should be so obstinate. (Have they already been obstinate or are they obstinate now?)
3 I don't know why he should go there tomorrow. (Correct in terms of grammar?)
4 I don't know why he should go there yesterday. (Correct in terms of grammar?)
One more thing, do the following unequivocally express the future reference?
5 I'm surprised that he should be going to say it tomorrow. (or I'm surprised that he should be saying it tomorrow.)
To tell you the truth, it's quite easy for me to interpret the first one either as an even which is going to happen in the future or as an even taking place in the past.
3 and 4 are also interesting, as the only difference they have is the words tommorrow and yesterday, by that I want to see whether SHOULD follows them in the time respect or it doesn't. Please comment on each example.