Calculate Previous Month Total When Two Dates Are Equal

[InfiniteSheldon]

I currently have 3 tables - sales, customer, date. For the date table, I am using the [Month End] column (always the last day of the month) on the 'Date Table' to filter the Sales table (see the screenshot below).

I have written a measure below to calcualte the total mobile sales when the transaction date equals the posting date:

Current Month Mobile Sales = 
Calculate(
Sum(Sales[Total Amount],
Customer[Customer_Type] = "Mobile",
Sales[Transaction Date] = Sales[Posting Date] 

)

How can I get the "previous month Mobile Sales"? I wrote the DAX below:

Calculate(
[Current Month Mobile Sales],

DATEADD('Date Table'[Month End], -1, MONTH)
)

However, it only works when there are 31 days in a month. How should I fix it to get the correct "previous month Mobile Sales" when filtering by the [Month End] column?

Thanks! 

[some_bih]

Hi @InfiniteSheldon did you try DAX function TOTALMTD? Hope this help

https://learn.microsoft.com/en-us/dax/totalmtd-function-dax?WT.mc_id=DP-MVP-4025372 

[InfiniteSheldon]

Hi @some_bih, could you please be more specific? I am not sure how TOTALMTD is going to help calculate previous month total when two dates are the same. 

[some_bih]

Hi @InfiniteSheldon 

Apply as measure X=TOTALMTD(

[Current Month Mobile Sales], 'Your Date table date column key')

Check result. Hope this help

[InfiniteSheldon · Accepted solution]

Hi @some_bih, I don't think that's the solution. However, I figured it out myself using 

PREVIOUSMONTH rather than DATEADD('Date Table'[Month End], -1, MONTH). Thanks anyway for your help!