DAX: Previousmonth / parallelperiod / dateadd doesn't work

[RemiAnthonise]

I've made a table and I've added some fields to calculate total sales per month and Month over month compare, see image below.

I've used these formulas:

Total Sales = SUM(ProjectPostTransViews[TotalSalesAmount])

Total Sales vorige maand = CALCULATE(ProjectPostTransViews[Total Sales]; PARALLELPERIOD('Calendar'[Date]; -1; MONTH))

Total Sales vorige maand2 = CALCULATE(ProjectPostTransViews[Total Sales]; PREVIOUSMONTH('Calendar'[Date]))

Total Sales vorige maand3 = CALCULATE(ProjectPostTransViews[Total Sales]; DATEADD('Calendar'[Date]; -1; MONTH))

Calendar table = Calendar = CALENDAR (DATE (2016; 01; 01); DATE (2025; 12; 31))

I've treied the 3 formulas to see if, in some case, the outcome is different. It's not. But that's not the problem. My problem is that the values for all 3 'last month' formulas are the same as the total sales value for that month. 

What am I doing wrong?

[gooranga1 · Accepted solution]

Hi @RemiAnthonise,

It looks like it's the TRansactionDate in your ProjectPostTransViews as it's a datetime field with a time of 12:00:00 midday. So when you link the Calendar table to it it will return no values as these are just the date that will assume midnight.

Create a new column in the ProjectPostTransViews table like;

TransactionDateOnly = date(year(ProjectPostTransViews[TransactionDate]),month(ProjectPostTransViews[TransactionDate]),DAY(ProjectPostTransViews[TransactionDate]))

then join on that.