Heh, got that calendar on my wall right now. Thanks for reminding me to switch it to November.

Is there any good reason to switch to past tense here? It seems awkward to me.

You're correct, the tense should be the same for the whole sentence. For what it's worth, that's something I have trouble with in my own writing, a lot. Because when I'm doing technical writing (such as for a FAQ ), doing a "for instance" example, it's hard to keep that sort of thing straight. I try to make myself go back over it and proofread for things like that, but sometimes I miss it.