Apart from the formatting issue, what does it really mean if one adds two dates together? Yeah, I can see that adding today's date and tomorrow's date as in

SELECT GETDATE()+GETDATE()+1

yields

2118-09-12 20:25:12.580

as off the moment I ran the query, since it's just treated like a floating point addition that then gets converted back to a datetime, but does it really make sense to attempt such a thing in the first place?

Anyhow, I got the answer wrong, but did learn something new since I was under the impression that converting a negative integer to a datetime would cause some kind of conversion error.