Calculating Previous without Contiguous date column but having start date and end date of week

tulasi_pbi1988 , Check how I have use week rank to deal with week

https://community.powerbi.com/t5/Community-Blog/Week-Is-Not-So-Weak-WTD-Last-WTD-and-This-Week-vs-Last-Week/ba-p/1051123

Date = CALENDAR(Date(2018,01,01),TODAY())
Mark as Date Table

Week Start date = 'Date'[Date]+-1*WEEKDAY('Date'[Date],2)+1
Week End date = 'Date'[Date]+ 7-1*WEEKDAY('Date'[Date],2)
Week Number = WEEKNUM([Date],2)
Week Rank = RANKX(all('Date'),'Date'[Week Start date],,ASC,Dense)
Week name = [Week Start date] & " to "& [Week End date]
Weekday = WEEKDAY([Date],2)

And use week in Rank

This Week = CALCULATE(sum('order'[Qty]), FILTER(ALL('Date'),'Date'[Week Rank]=max('Date'[Week Rank])))
Last Week = CALCULATE(sum('order'[Qty]), FILTER(ALL('Date'),'Date'[Week Rank]=max('Date'[Week Rank])-1))
Last 12 week Sales = CALCULATE(SUM(Sales[Net Sales]),FILTER(all('Date'),'Date'[Week Rank]>=min('Date'[Week Rank])-12 && 'Date'[Week Rank]<=max('Date'[Week Rank])))
Next 3 period Sales =
Var _min = maxx(allselected('Date','Date'[period Rank])
Var _max = maxx(allselected('Date','Date'[period Rank]) +3
CALCULATE(SUM(Sales[Net Sales]),FILTER(all('Date'),'Date'[Week Rank]>=_min && 'Date'[Week Rank]<=_max))

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