anniversary

1. A day that is an exact number of years (to the day) since a given significant event occurred. Often preceded by an ordinal number indicating the number of years.Examples: "We are celebrating our tenth anniversary today."especially

2. (loosely) A day subsequent in time to a given event by some significant period other than a year (especially as prefixed by the amount of time in question).Examples: "The occasion was the six-month anniversary of the Aug. 8 coup that brought General Óscar Humberto Mejía Victores to power."; "In a thinly veiled threat to Saddam Hussein, President George Bush marked the six-month anniversary of September 11th by reiterating America's commitment to prevent rogue countries obtaining weapons of mass destruction."; "Jonathon proposed to his [Jess's] mom on their three-month anniversary of meeting and married her on their fourth."broadly