B1
the day on which an important event happened in a previous year
Dictionary examples:
For their work anniversary, they gave each other high fives and went home. (0.0)
On the anniversary of buying his guitar, he finally learned one chord. (0.0)
On the anniversary of his diet, he ate an entire cake. (0.0)
We always celebrate our wedding anniversary with dinner at an expensive restaurant. (28.2)
Tomorrow is the fiftieth anniversary of the revolution. (62.3)