"Yo vuelvo a España el veinte de junio."
Translation:I return to Spain on June twentieth.
Perhaps the DL program was trying to elicit the alternative translation of "I am returning to Spain on June twentieth."
That's what I wrote, but Duo did not like it. They wanted "I go back..."
Personally, I see no difference among "I go back", "I come back" and "I return". They mean the same thing!
It marked twentieth June wrong for me just now. I would prefer to say on the twentieth of June. I wonder if that is a UK English construction. How would US or OZ English speakers say it?
Native US English speaker here, Southern Appalachian dialect, also having lived in Maine, Alaska, and Arizona.
You don't hear the structure of "twentieth June" much here—not unless you're watching BBC America or British TV on PBS anyway (or hanging out with anglophiles). I would say either "June twentieth" or "the twentieth of June". "June twentieth" is probably more common in daily speech, and "the twentieth of June" would be more commonly used in documents or formal speech.