Wow, this forum's dead...pun intended. I guess I don't post much either. I don't know why, I love it. Anyway...
I consider the song to be in G maj but switching quickly to C maj for the "gonna miss" part.
I play D mixolydian, which I just consider G anyway, but it helps the phrasing considering the progression starts on D. Then switch to a C maj diatonic type scale for gonna miss part, then resolve back to D. You can wiggle around in the B pentatonic but you will not identify the key much.
Information is not knowledge. Knowledge is not wisdom. Wisdom is not beauty. Beauty is not love. Love is not music. Music is the best.- the girl from the bus