hour_shift can't be NaN anymore

baby steps to clean up code readability

Change-Id: I43a2b2a6b046068214de32dd3853ab87a8f5df71
Reviewed-on: https://gerrit.instructure.com/31594
Reviewed-by: Stanley Stuart <stanley@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Jacob Fugal <jacob@instructure.com>
QA-Review: Jacob Fugal <jacob@instructure.com>