Once yearly is called yearly.
No, you are not an alcoholic if you get drunk once a year and you are not an abuser if you call someone a name once every five years.
A year.
An annual event
a year, or one earth revolution
Molting
state of the union address
Every year I think
Once a year is correct.
365.24 days. We have a special name for that period of time. We call it a "year".
Roughly 3651/4 days. It's the period of time that we call a "year".
The league of Nations met once a year
Muster day is a once a year thing where they would take roll call of all the troops in the early 1700's