"Only once a year?"
Translation:Einmal jährlich nur?
What is wrong with "Einzig einmal im Jahr?"; can "einzig" not be used here?
Edit: I believe I've figured it out. It looks like "einzig" is generally used as an adjective (e.g. the only/sole person), while "nur" is only used as an adverb (e.g. the only tall person).
Apparently "einzig" can be used as an adverb (or at least could have been at one point) according to dict.cc, but it appears to be uncommon to such an extent that I would bet it is considered awkward/unnatural to native speakers.