When installing hrabsence, CRM_HRAbsence_Upgrader::install() should check to see if any absence periods have been defined. If not, then a new period should be created based on the current calendar year (whatever that year is), e.g.
- Name: 2014
- Label: 2014
- Start Date: 1 Jan 2014
- End Date: 31 Dec 2014
When installing with generated sample data, this could lead to duplicate HRAbsencePeriods. GenerateHRData should pre-emptively remove any HRAbsencePeriods to prevent such duplicates.