ensure calendar events API uses correct date times part 1

refs CNVS-9618

test plan
 - calendar events INDEX request will not change
 - when passing a negative year "-0001-12-26" it
   will create an error report

Change-Id: Iaccc1a171cb60c686954ae7a3138b797521becb2
Reviewed-on: https://gerrit.instructure.com/32861
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Anthus Williams <awilliams@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>