How to obtain YTD value for one month prior BUT if January, then just last December of prior year?

[VocationSmart]

I am wanting to calculate YTD for a parrallelperiod, in this case prior month.  The equation is straight forward but where I run into trouble is when the current period is January, then it I get YTD for the entirely of the prior year (since the one month prior to January is Decembe of the prior year).

So what I want is if the month is January, then for the measure to return the value for December of the prior year.

This is what I currently have.

NewAccounts YTD LastMonth =

CALCULATE(

SUM( Production[NewAccounts] ),

DATESYTD( PARALLELPERIOD( 'CalendarAuto'[Date], -1, MONTH ) ),

)

I've tried using an IF() statement but PowerBi won't recognize a date table/filed in an IF() statement

[VocationSmart · Accepted solution]

I solved this by limiting the minimum date witin the date table:

CALCULATE(

   SUM( QryProduction_3yrs[NewAccounts] ),

   DATESYTD( PARALLELPERIOD( 'CalendarAuto'[Date], -1, MONTH ) ),

   FILTER(

      ALL('CalendarAuto'[Date]),

      'CalendarAuto'[Date] <= EOMONTH( TODAY(), -1) -- date maximum

         && 'CalendarAuto'[Date] >= DATE( YEAR( TODAY() ) -1, 12, 1) -- date minimum 

   )

)