Compare week in different years

Anonymous 

Typically same week is 364 days behind

Week Year behind Sales = CALCULATE(SUM(Sales[Sales Amount]),dateadd('Date'[Date],-364,Day))

You can also refer this file which use week rank -https://www.dropbox.com/s/d9898a48e76wmvl/sales_analytics_weekWise.pbix?dl=0

The same week would be 52 ranks less  or you can use

Also you can modify this formula and use

Measure TD = 
var _max = maxx(table[Week])//format of 201901
var _week = right([WeekYear],2)
var _year= left([WeekYear],4)
return
calculate(table[Value], filter(all(Table), Table[Year]=_year && Table[week No] <=_week))

Measure LTD = 
var _max = maxx(table[Week])//format of 201901
var _week = right([WeekYear],2)
var _year= left([WeekYear],4)-1
return
= calculate(table[Value], filter(all(Table), Table[Year]=_year&& Table[week No] <=_week))