'Good day!' in Swedish is 'god dag' (~good duhg). As might happen perhaps even in most of the natural languages of this planet, pronunciation of frequently used expressions becomes "lazier", so to speak.
That's happened to 'god dag', too! So, perhaps the most common pronunciation is, in phonetic spelling 'gudaa' (~ goo-duh). As it happens, 'guda' in Sanskrit means 'anus', etc! LoL and go figure!
