"I left the pub at nine o'clock."
Translation:Es i o'r dafarn am naw o'r gloch.
That is its literal meaning, but it is not a common way of putting it in English. As Welsh has some very different patterns from English it is not always straightforward to translate between them while avoiding sounding awkward or old-fashioned.
'Gadelais y dafarn am naw o'r gloch' would be more appropriate for formal Welsh.
This course does not use formal Welsh at all, not is it accepted in the answers. (Gadawais y dafarn... would be the correct form from gadael - it has an irregular stem.)
We do accept Gadawais i'r dafarn..., though.
Camgymeriad ar fy narn. Fedrai dallt pam nad oes yna bwyslais ar y Cymraeg ffurfiol, ond dwi'n falch rydych yn ei cymryd fel ddewis.