A day set aside to commemorate or remember a person or event; an anniversary (e.g., wedding anniversary, founding day).
明日は私たちの結婚記念日だからレストランを予約した。
Tomorrow is our wedding anniversary so I booked a restaurant.
会社の創立記念日は毎年社員全員で式典を開く。
On the company's founding anniversary, all employees hold a ceremony every year.
彼は学校の記念日に講演を頼まれた。
He was asked to give a speech on the school's anniversary.