Schedule:FixedInterval - How to define design day behavior?

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Until Schedule:File is supported in OpenStudio, I've been creating Schedule:FixedInterval for stuff like load profiles (8760-schedules, or more granular, see relevant question Can you load Schedule:File in OpenStudio?).

I just ran into a case where my load profile is zero for January 15, which happens to be my design day condition for winter. As a result, my loop is getting sized to zero.

I've looked at the source code for ScheduleFixedInterval and its abstract base class (ScheduleInterval), but I can't seem to find anything that will allow me to set the design day behavior. Am I missing something? Or is the feature just missing from OpenStudio?