Shouldn't it be "happy day" instead of "lucky day"? Is that a correct collocation or a tiny mistake?
It is accepted as well and I do not see anything wrong with a lucky day. In "my lucky day" it is even much more common than "my happy day" although the meaning differs, at least for me as an ESL speaker.
It would be happy if it was a literal translation bu the meaning is lucky :)
A "happy-go-lucky" translation!