fix edge case duration roundings
Created by: JonRowe
Based on the work of @fabersky but with @myronmarston's spec. Supersedes and fixes #2187.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Created by: JonRowe
Based on the work of @fabersky but with @myronmarston's spec. Supersedes and fixes #2187.