DWH time slices show
different min and max dates on PPM schema vs min/max dates on DWH (dwh_com_periods table.)
 
Example queries:  
PPM Schema:
select min(SR.FROM_DATE),
             max(SR.TO_DATE)
from prj_blb_slicerequests sr
where SR.IS_DWH_REQUEST = 1

DWH schema:
select min(period_start_date),
             max(period_end_date)
from DWH_CMN_PERIOD

Why don't the end dates match?  Should they?

Release:
Component: PPMTSL

In order get get the periods for the DWH there are other criteria taken into consideration.

The query you should compare on PPM schema is 

select min(period_start_date), 
MAX(PERIOD_END_DATE) 
from DWH_CMN_PERIOD_V 

If you then review the SQL behind this view you will see it looks at items such as fiscal periods (biz_com_periods) and data in rpt_calendar table in addition to the actual DWH slices in the Time Slices page.