The letter e.
The letter "e" because its twice in lifetime, once in year, twice in week, and never in a day
The letter E
Two drops twice a day.
e
twice-a-day or it can be called semi-diurnal which relates to such occurrences as tides.
The letter DDAYDECADECENTURY
The letter e.
The letter E appears twice in wEEk, one in yEar, but not in day.
The letter E. It is in the word 'week' twice, the word 'year' once and it's not in the word 'day.'
The letter e.
The letter DDAYDECADECENTURY
the letter e
Twicw a dah
if you have problem in blood circulating your penis just go into the bed and mustubate (handing).
That happens twice, at the "equinoxes".
If this is a riddle the answer is the letter 'e'. 2 times in wEEk. Once in yEar. there are no 'E's in day.