Hello. Please tell me why the two calculated fields have different time calculation (more than 2 times). In my opinion they should not vary in speed:
SUM(MTD(StrToMember ('[Kalendar].[Kalendar].[Data_Sales].&['+format( DateAdd("yyyy", -1, now()), "yyyy-MM-dd" )+'T00:00:00]') ),[Measures].[Sales])
SUM(MTD(StrToMember ('[Kalendar].[Kalendar].[Data_Sales].&[2014-08-26T00:00:00]') ),[Measures].[Sales])
SUM(MTD(StrToMember ('[Kalendar].[Kalendar].[Data_Sales].&['+format( DateAdd("yyyy", -1, now()), "yyyy-MM-dd" )+'T00:00:00]') ),[Measures].[Sales])
SUM(MTD(StrToMember ('[Kalendar].[Kalendar].[Data_Sales].&[2014-08-26T00:00:00]') ),[Measures].[Sales])