So that's what happened. I noticed I couldn't open Calendar on my phone - it starts to open and then just shuts down.
I really like the Windows Phone OS. I'm pissed off with Microsoft for dropping it. They may not have had as much initial success with it as they liked but it is a solid OS and ceding the market entirely to Google and Apple is a huge mistake. I've stuck with it since because I like it, but I'm going to have to get an Android phone soon just because nobody writes software for WP anymore.