http://www.sqlservercentral.com/blogs/useful-information-and-case-studies-covering-data-warehousing-data-modeling-and-business-intelligence/2013/02/07/ssas-how-to-create-dynamic-time-calculations-to-reuse-over-any-measure/

SSAS How-To: Create Dynamic Time Calculations To Reuse Over Any Measure

By sal.deloera, 2013/02/07

Rather than making individual time calculations for each measure in an SSAS cube (i.e. YTD, Prior YTD, YTD Variances, etc), one can use a more dynamic approach to time calcs applicable to all measures and save a great amount of dev time and overhead in the process.

1. Create Named Query in DSV:

2. Create the dimension and add it to the Dimension Usage tab of the cube (no relations to the fact will exist)

3. Add the MDX script calculations:

SCOPE (

[Date].[Calendar Hierarchy].MEMBERS);

[Date Calculations].[Date Calculations].[YTD] =
AGGREGATE
(

    {[Date Calculations].[Date Calculations].[Selected Date]} *
     PERIODSTODATE
     (
       [Date].[Calendar Hierarchy].[Calendar Year],
       [Date].[Calendar Hierarchy].CURRENTMEMBER
     )
);

[Date Calculations].[Date Calculations].[PY YTD] =
AGGREGATE
(
   {[Date Calculations].[Date Calculations].[Selected Date]} *
   PERIODSTODATE
   (
      [Date].[Calendar Hierarchy].[Calendar Year],
      PARALLELPERIOD
      (
         [Date].[Calendar Hierarchy].[Calendar Year],
         1,
         [Date].[Calendar Hierarchy].CURRENTMEMBER
   )
)
);

END SCOPE;

SCOPE ([Date].[Calendar Hierarchy].[All]);

[Date Calculations].[Date Calculations].[YTD] = NULL;

[Date Calculations].[Date Calculations].[PY YTD]=NULL;

END SCOPE;

[Date Calculations].[Date Calculations].[YTD Chg]=[Date Calculations].[Date Calculations].[YTD]-

[Date Calculations].[Date Calculations].[PY YTD];

[Date Calculations].[Date Calculations].[YTD Chg %] =
IIF
(
[Date Calculations].[Date Calculations].[PY YTD] = 0,
NULL,
([Date Calculations].[Date Calculations].[YTD] - [Date Calculations].[Date Calculations].[PY YTD]) /
[Date Calculations].[Date Calculations].[PY YTD]
);

FORMAT_STRING([Date Calculations].[Date Calculations].[YTD Chg %]) = “#,0.0%”;

//Create current year and month in scripts:
CREATESET CURRENTCUBE.[Current Year]
AS {(strtomember(“[Date].[Calendar Hierarchy].[Calendar Year].["+ cstr(year(now()))+"]“))}, DISPLAY_FOLDER = ‘Named Sets’ ;

CREATESET CURRENTCUBE.[Current Month] AS
TAIL
(
NONEMPTY
(
[Date].[Calendar Hierarchy].[Month Name Year],
[Measures].[Fact Sales Count]
)
);

The result!