Conpherence - fix off by one bug in calendar data fetching

Summary: Ref T3155. "last sunday" is "last sunday at 00:00" so you have to include a day for Sunday itself.

Test Plan: calendar renders correctly today - saturday - which is the edge case of this

Reviewers: epriestley, chad

Reviewed By: chad

CC: aran, Korvin

Maniphest Tasks: T3155

Differential Revision: https://secure.phabricator.com/D6108