 
       fakePeriodDisable(element, disabledPeriod)
       fakePeriodDisable(element, anotherDisabledPeriod)
-      element.setOpensAt(new Date(dayAfter), period)
+      element.setOpensAt(getISODateString(dayAfter), period)
 
       opensAt = TaskPlanStore.getOpensAt(NEW_READING.id)
       expect(opensAt).to.not.be.ok
 
       opensAt = TaskPlanStore.getOpensAt(NEW_READING.id, period.id)
-      expect(getDateString(opensAt)).to.be.equal(getDateString(dayAfter))
+      expect(getISODateString(opensAt)).to.be.equal(getISODateString(dayAfter))
 
   it 'can update due date for individual period', ->
     period = COURSES[0].periods[0]

  it 'sets the default due date when based on query string', ->
    helper(NEW_READING, {due_at: getISODateString(dayAfter)} ).then ({dom, element}) ->
      dueAt = TaskPlanStore.getDueAt(NEW_READING.id)
      expect(getDateString(dueAt)).to.be.equal(getDateString(dayAfter))
      expect(dom.querySelector('.-assignment-due-date .datepicker__input-container input').value)
        .to.be.equal(getDateString(dayAfter))

      element.setIndividualPeriods()

      #set due dates to be different
      element.setDueAt(getISODateString(tomorrow), firstPeriod)
      element.setDueAt(getISODateString(dayAfter), secondPeriod)

      #set all periods
      element.setAllPeriods()
