Fix day view start hour

Summary: Ref T8308, Fix day view start hour

Test Plan: Day views start at 8am OR hour of first event start time if there is an event scheduled before 8am on that day OR midnight if there is a non-all-day multi-day event carried over from the previous day

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T8308

Differential Revision: https://secure.phabricator.com/D13013