Regarding the DATEADD working with modifier ALL('Date')

Hi all,
I have a normal model with 'Date' and 'Sales' tables. And I have 3 measures,

1. The first one is Sales Amount := SUMX('Sales', [Quantity] * [Net Price])
2. The second one is Sales AllDate := CALCULATE( [Saltes Amount], ALL('Date'))
3. The last one is Sales PM in AllDate := CALCULATE( [Saltes Amount], DATEADD('Date'[Date], -1 ,MONTH), ALL('Date'))

I put them in a matrix, but I don't understand the behavior of the last measure, why the ALL modifier doesn't remove the filter of DATEADD? It's like the measure of CALCULATE( [Saltes Amount], DATEADD('Date'[Date], -1 ,MONTH))
Could someone please explain it to me. Thanks!