A Day To Remember
From Halopedia, the Halo wiki
A Day To Remember is an achievement in Halo: The Master Chief Collection. It is unlocked by playing Halo: Combat Evolved on the 15th of any month - the day in November 2001, when the original game was released. The achievement will unlock as soon as the player begins a campaign mission or multiplayer match. The achievement is worth 5 Gamerscore.