R1:d816ac0b01d7

Fixing some calendar event timeline issues.

Summary: Ref T7953, Fixing some calendar event timeline issues.

Test Plan: Create event, event timeline should reflect the transaction.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7953

Differential Revision: https://secure.phabricator.com/D12592