April riddle

Here’s a little light riddle for the week. In medieval Europe, April was the first full month of the New Year, which began on March 25 — the feast of the Annunciation for Western Christians. Tolkien borrowed this date as the day of the Ring’s destruction in Mount Doom, and Aragorn instituted it as the beginning of the Gondorian New Year.  So it seems appropriate to seize the day (well, about a week late) to post a short riddle about time.

The answer will appear in a comment on Friday.

I only appear
Once in a year.
Wherever you seek,
I’m twice in a week.
And I’m sorry to say,
I’m not once in a day.