LeavePeriod:
  0: { leavePeriodId: 1, startDate: '2008-02-01', endDate: '2009-01-31' }
  1: { leavePeriodId: 2, startDate: '2009-02-01', endDate: '2010-01-31' }
  2: { leavePeriodId: 3, startDate: '2010-02-01', endDate: '2011-01-31' }