If you say you’ll get something done today, what do you mean?

Do you mean you’ll have it done by close of business?

Do you mean you’ll have it done by midnight?

Do you mean you’ll have it done before you go to bed, which could be 2 am tomorrow morning?

Depending on what you’re getting done the answer could be any of the three options. It only matters that you know which is appropriate and get it done by the deadline.