Anyway, I looked up on GodChecker.com "anniversary." This is what I got:
HE-BO: God of the Yellow River.
Although the Great DA-YU took care of the Great Flood, the Yellow River was still prone to flooding. So an enthusiastic mortal named HE-BO tied heavy rocks to his back and jumped into the water as a supreme sacrifice.
For his pains he was granted immortality and promoted to God of the Yellow River.
Following his example, it became the custom to throw a young virgin into the river on the anniversary of his death. This practice appears to have died out.
Now, that was interesting and all, but it gave a deathly pall to the whole thing and wasn't quite what I was hoping for. I don't know what I expected. I was hoping to find some Baltic goddess that goes by the name Anniversia who has some ritual for wedding anniversaries or something. Alas, it was not to be.
It did remind of the old joke: Did you read the book Yellow River by I. P. Freely?
Childish, I know. Did you really expect any different?