I don't know why my brother hasn't been fired yet

so, today my brother's boss told him "You have until April to complete the project."

and my brother doesn't know what expression he gave but his boss went on to tell my brother that 'until April' included all of March and the last week of February.

My brother started to laugh and his boss asked "What?!"

My brother said "By the last week in February, you mean Monday"