Do You Remember When We Met
From Halopedia, the Halo wiki
Do You Remember When We Met is an achievement in Halo: The Master Chief Collection. It is unlocked by playing Halo 3: ODST on the 22nd of any month - the day in September 2009 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.
The achievement's name may be a reference to a lyric from the song Sea of Love.