Past 3 months selected date

[Easley06]

Hi,

i already have the Past 3 month average of the lastdate 

current measure : 

Gross P3 1 = CALCULATE(SUM(FACT_OFF_TAKE[GROSS_AMT]), DATESINPERIOD(DATE_SYSTEM[DATE],

LASTDATE(PREVIOUSMONTH(LASTDATE(DATE_SYSTEM[DATE]))), -3,MONTH),

ALL(DATE_SYSTEM[MONTH_NAME],DATE_SYSTEM[MONTH],DATE_SYSTEM[YEAR])) / 3

But i need to get the start date of these Dates 

measure used = 

Gross P3 2 = CALCULATE(SUM(FACT_OFF_TAKE[GROSS_AMT]), DATESINPERIOD(DATE_SYSTEM[DATE],

LASTDATE(PREVIOUSMONTH(LASTDATE(HOME_RESELLER[TRAINING_DT]))), -3,MONTH),

ALL(DATE_SYSTEM[MONTH_NAME],DATE_SYSTEM[MONTH],DATE_SYSTEM[YEAR])) / 3

thanks.

[amitchandak]

@Easley06 , You should use date table joined with date of your table

example

3 Month Avg = CALCULATE(AverageX(Values('Date'[MONTH Year]),calculate(Sum(FACT_OFF_TAKE[GROSS_AMT])))
,DATESINPERIOD('Date'[Date ],MAX('Date'[Date ]),-3,MONTH))

Rolling Months Formula: https://youtu.be/GS5O4G81fww

Average of Rolling, Average of Snapshots: https://youtu.be/_pZRdLAJxxA

If you need 3 month on axis

Need of an Independent Date Table:https://www.youtube.com/watch?v=44fGGmg9fHI