I am an indian. Today I called a receptionist. She told me that I must submit my form by today. I was shocked and so I said "What?Today itself?" She said "Yes today only" I know both of us are wrong grammatically.Natives dont say today itself/today only.So what I(and She) should have said?
"Today only" means "Today is the only day that you can submit it." You will often find it in advertising: "Today only! All fish at half price!"
I would think any of these would work:
"Really? By the end of today?"
"Really? Tomorrow will be too late?"
"Really? Before the end of the day?"
Of course, this opens another can of worms; namely, when is the end of the day?
Midnight is one valid answer, but before closing time might also be correct, particularly in an office setting. When the latter applies, you can also use:
"Really? Before close of business?"
In email exchanges, you might see that written as "before COB today."