%Change YoY (problem wth calculation)

[Vosina]

Hi everyone, 
in spite there ale quite a lot of videos and descriptions, I have not been able to get to the result I desire with comparing date across years. I have 1 data table with multiple sales in a month and 1 lookup date table. Relation between them is build.
The problem is if I compare 2018 and 2019 data, %change calculates with months in 2018 which have not occured in 2019 yet (makes it -100% these months).
This approach got me farthest but still the TOTALS are wrong.
1) Created ThisYear Measure = ThisYear = SUM([Sales] )
2) Created LastYear Measure = CALCULATE(Sales[ThisYear];SAMEPERIODLASTYEAR(Kalendar_Lookup[Datum].[Date]))
3) Created LasYear_cleared Measure= 

IF(ISBLANK(SporeniObjem_Kanaly[SporeniObjemCalc]);BLANK();CALCULATE(Sales[ThisYear];SAMEPERIODLASTYEAR(Kalendar_Lookup[Datum].[Date]))) .... with hope those data which do not have 2019 counterparts will not be calculated. Works in the table view but Sum is still the Same as LastYear 😕
4) Created %Change Measure = IF(OR(ISBLANK([LastYear_cleared]);ISBLANK([ThisYear]));BLANK();([ThisYear]/[LastYear_cleared]-1)) ... with the same aim as in Point 3)
The result is that Total shows -51,77% but it should show something like -20,2%. This miscalcuation of course shows in other views and tables for reps

Can you please advise what I am doing wrong. Thank you so much

M.

[Greg_Deckler]

See if my Time Intelligence the Hard Way provides a different way of accomplishing what you are going for.

https://community.powerbi.com/t5/Quick-Measures-Gallery/Time-Intelligence-quot-The-Hard-Way-quot-TIT...

[Vosina]

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@Greg_Deckler wrote:

See if my Time Intelligence the Hard Way provides a different way of accomplishing what you are going for.

https://community.powerbi.com/t5/Quick-Measures-Gallery/Time-Intelligence-quot-The-Hard-Way-quot-TIT...

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Thank you Greg.  Gave me some time to figure it out but I managed to enter the Dax you suggest. I got somewhere with the ThisYear formula but the LastYear gives me no values, thus %change does not work either. Would you suggest what I am doing wrong?
1. I have got separate Date table (Kalendar_Lookup) with all dates available in the calendar and calucalted columns with Year and Month. 
2. My data table includes Date (1st day of the month) + Value, there are multiple rows with the same date for multiple Sales reps. (normalized)
Another problem I see here is, that I will not recieve %Change 2017/2018 by this formula

Thank you so much

M.