Compare different years measures with a month slice

[RPAI2812]

My database consists of monthly emissions data from three different years (2020, 2019 and 2018).

I've created three measures to filter the total emissions for each year a forth to compare emissions between 2020 and 2018: 

Total 2018 = CALCULATE(Emissions,YEAR('Date'[Date])=2018)
Total 2019 = CALCULATE(Emissions,YEAR('Date'[Date])=2019)

Total 2020 = CALCULATE(Emissions,YEAR('Date'[Date])=2020)

Var 2020-2018= [Total 2020] - [Total 2018].
However, I want to have be able to add a month slicer to my dashboard. That is, I want to be able to compare for instance 2020 and 2018 on Jan + Feb + Mar, or any other months combination that I select. But, when I do so and select the months on this slicer, the result from any of these 4 measures does not change. All I can get is the full year comparison.

[AlexisOlson · Accepted solution]

The conditions within CALCULATE remove and replace the existing filter context, so slicing on month doesn't change anything since that filter gets replaced.

Try wrapping the conditions with KEEPFILTERS to preserve existing filters.

Total 2018 = CALCULATE ( Emissions, KEEPFILTERS ( YEAR ( 'Date'[Date] ) = 2018 ) )

[RPAI2812]

It worked perfectly! 

Thank you very much!