calculate not working if criteria is measure

[Anonymous]

Hi
Can anyone please explain, why this measure is not working as expected (MTD_on_measure)?
(There is a reaason why MTD is calculated this way)
These are the dax expressions:

TotalSales = SUM('Table'[Sales])

month_start (Measure) =
var latest_date = CALCULATE(max('Table'[Date]),ALLEXCEPT('Table','Table'[Date]))

var month_start_date = latest_date - day(latest_date) +1

return month_start_date

MTD_on_measure =
CALCULATE([TotalSales],filter('Table',[Date]>=[month_start (Measure)]))

MTD_not_on_measure =
CALCULATE([TotalSales],filter('Table',[Date]>=date(2019,12,1)))

check_equality =
date(2019,12,1) = [month_start (Measure)]

[Anonymous]

@Anonymous In case you want MTD_on_measure to be same as MTD_noy_on_measure please create a measure as per below 

MTD_on_measure = 
var latest_date = CALCULATE(max('Data'[Date]),ALLEXCEPT('Data','Data'[Date]))
var month_start_date =  latest_date - day(latest_date) +1
RETURN CALCULATE(SUM(Data[Sales]),filter(ALL('Data'[Date]),[Date]>=month_start_date))

[Anonymous]

@Anonymous  thank you for your comment.

I should have probably mentioned it in the post that In my report I have a date slicer that changes current date and therefore MTD needs to be recalculated, so ALL would not fit in my case. I found a solution by simply copying Date column and using it instead, however I was rather seeking for an explanation why it was not working to understand DAX better.