MDX Get DAY value from Date Dimension, ROW Level

Hi

New to MDX, probably an easy one; How do I extract the Day from a Date at ROW level, I tried via using a Measure but the performance causes an out of memory to be thrown

SQL Example

DATEPART(DD,GETDATE())

Can I generate a ROW where I have  -->> CODE here , I just need help with the Syntax

//WITH MEMBER [Measures].[What Day] as 'DAY([Full Date])'

SELECT

     NONEMPTY {

//                [Measures].[What Day], 

                 [Measures].[Activation Success] } ON COLUMNS,

       NON EMPTY { (

  -->> CODE here   DAY([Activation UTC Date].[Activation Calendar Date].[Activation Calendar Date]) * 

                       [Activation UTC Date].[Activation Calendar Month Name].[Activation Calendar Month Name].ALLMEMBERS *

                             [Activation UTC Date].[Activation Calendar Year Name].[Activation Calendar Year Name].ALLMEMBERS *

                             [Licensable Product].[Licensable Product Name].[Licensable Product Name].ALLMEMBERS *

                             [Activation Geography].[ISO Country Code].[ISO Country Code].ALLMEMBERS *

                             [Activation Geography].[ISO Country Name].[ISO Country Name].ALLMEMBERS *

                             [Licensable Product].[Licensable Product Family Name].[Licensable Product Family Name].ALLMEMBERS *

                             [Sold To OEM Partner Account].[Sold To OEM Partner Account ID].[Sold To OEM Partner Account ID].ALLMEMBERS *

                             [Sold To OEM Partner Account].[Sold To OEM Partner Account Name].[Sold To OEM Partner Account Name].ALLMEMBERS

                       ) }

                       DIMENSIONPROPERTIESMEMBER_CAPTION, MEMBER_UNIQUE_NAMEONROWS

                       //FROM(SELECT ( STRTOSET(@ProductFamilyCode) ) ON COLUMNS

                       FROM [cubeOAMart]

                 //    )

                       CELLPROPERTIESVALUE, BACK_COLOR,FORE_COLOR, FORMATTED_VALUE,FORMAT_STRING, FONT_NAME,FONT_SIZE, FONT_FLAGS