Er, that would be first and third Wednesdays. If I was talking about it, which I'm not.

Changing key isn't necessarily a sign of incompetence, incidentally - most unaccompanied singers tend to drift up over the length of a song, sometimes quite noticeably. (You can hear the great Tony Rose drifting off-pitch on his version of the Golden Vanitee - although the chorus singers are having none of it and quickly drag him back down.)