"I was there for a year."
Translation:Dw i 'na ers blwyddyn.
This doesn't need a past tense verb? I would assume this meant "I have been here for a year" (implying i'm still here).
That is correct, for me "I was there for a year" would be "Roeddwn i yna am flwyddyn" (or other ways of phrasing it.