four months
Refers to a duration of four months. Not to be confused with 四月 (しがつ), which means 'April'.
このプロジェクトは四月かかる予定です。
This project is scheduled to take four months.
四月ぶりに故郷へ帰った。
I returned to my hometown after four months.
It took four months for this construction to be completed.