R1:b1e44239ba11

Fix calendar display on profile.

Summary:
...maybe anyway because I can't reproduce it live. This diff does two things that should help with bugginess though - uses $viewer rather than $user (...$user is who we are looking at...) *AND* upgrades a Conpherence util class to Calendar, and said util class has unit tests and came about from fixing a similar bug in Conpherence back in the day.

Wrote some comments in the util class because I think it has a tendency to trip people up. These comments are not…