if u have a Year field:
sum({<Date,Year={'2019'}>}Measure)
or
sum({<Date,Year={"$(=max(Year))"}>}Measure) // shows the max year : 2019, but if u select 2018, 2018 would be the max of 2018, so this depends on the selection
or
sum({<Date,Year={"$(=max({1}Year))"}>}Measure) //always show 2019 (max year) no matter the selection ( the {1} part does this)
Please, seach for tutorials on set expression- Qlik
ps: if u have only Date field :
1) create a year field in the script and use it : Year(Date) as Year
2) use this expression
sum({<Date={">=$(=YearStart(max(Date)))"}>}Measure) // depends on the selection
or
sum({<Date={">=$(=YearStart(max({1}Date)))"}>}Measure) // does not depend on the selection
