There seem to be a lot of questions about "Can I have more than one tense in a sentence?" (e.g. I ordered a product on saturday and it has been delivered as well)
I'm wondering if there's any particular reason for this, and if maybe we should have a canonical post for it.
Do other languages not let you do this? (I'm pretty sure this is not generally the case. In all of the languages I have direct experience with, you can do it. Not sure about languages like Mandarin, which don't really have tenses like English does.)
Is there some specific piece of guidance, a book or a website or something, out there which gives the impression you can't?
Are there just a lot of crappy teachers of English out there?