Translation:A driver will come the day after tomorrow
In British English it is always "the day after tomorrow".
That's what I usually say, but the given answer is technically still correct. If they don't accept both then that's a problem
Do you mean in a particular dialect? I can't think how it is technically correct if no one says it that way.
There is only one possible day after tomorrow, so it has to be the definite article "the". We only use the indefinite article "a" when referring to one of several items, e.g. "a day in my life". This is the distinction that is missing in Swahili.
in the sense that it is grammatically correct. A day after tomorrow and the day after tomorrow mean the same thing