He attacked the enemy's position using a grenade launcher.

He was studying all day.

I am studying for the Japanese Language Proficiency Test next year.

He has fundamental knowledge of mathematics.

His recovery was truly miraculous.

He tried to solve the problem all day long.

Today is my birthday.

Our store has a regular day off every Monday.

Our project is scheduled to be completed on the twentieth day of the month.

Day after day, he continued to strive to solve the problem.