Yes, by the end of today is correct. It's not a complete sentence, though.
Wednesday morning, it is correct to say I have not seen him for one day. Wednesday afternoon, or by working day end, it is correct to say I have not seen him for two days
yes
Yes, you can say that; we've got today to get this job done.
It is not, but it is widely used because it conveys the general idea of the question as well as its grammatically correct version.No you should say "Where are you" the at at the end is not needed.
"Did he come today ?" is correct
Today is already implied at nights end & no need to add. Just say "I had a great evening".
say it will end "badly."
It is grammatically correct to say , "I am in school today." This is because you are in the building, not at the building.
Neither is correct. We say "at the end of August."
Wednesday morning, it is correct to say I have not seen him for one day. Wednesday afternoon, or by working day end, it is correct to say I have not seen him for two days
yes
Yes, you can say that; we've got today to get this job done.
Yes.
Yes, the possessive form of the noun week is the correct form for 'the end of the week' (the week's end).
Tag questions can end in it. That's correct, isn't it? or That's not correct, is it?
Yes that is correct.
It is correct, but it would be nicer to use the baby's name, as in "How is Johnny today?"