Rolling 4 weeks calculation

Anonymous , refer my blog for 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

Columns in 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 = if('Date'[Week Number]<10,'Date'[Year]*10 & 'Date'[Week Number],'Date'[Year]&'Date'[Week Number])
Week Rank = RANKX(all('Date'),'Date'[Week Start date],,ASC,Dense)
Week name = [Week Start date] & " to "& [Week End date]
Weekday = WEEKDAY([Date],2)
WeekDay Name = FORMAT([Date],"ddd")

Measures

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))
rolling 4 week Sales = CALCULATE(SUM(Sales[Net Sales]),FILTER(all('Date'),'Date'[Week Rank]>=min('Date'[Week Rank])-4 && 'Date'[Week Rank]<=max('Date'[Week Rank])))

Last 4 period Sales =
Var _min = maxx(allselected('Date','Date'[Week Rank]) -4
Var _max = maxx(allselected('Date','Date'[Week Rank]) 
CALCULATE(SUM(Sales[Net Sales]),FILTER(all('Date'),'Date'[Week Rank]>=_min && 'Date'[Week Rank]<=_max))

To get the best of the time intelligence function. Make sure you have a date calendar and it has been marked as the date in model view. Also, join it with the date column of your fact/s. Refer :
https://radacad.com/creating-calendar-table-in-power-bi-using-dax-functions
https://www.archerpoint.com/blog/Posts/creating-date-table-power-bi
https://www.sqlbi.com/articles/creating-a-simple-date-table-in-dax/

My Webinar :

https://community.powerbi.com/t5/Webinars-and-Video-Gallery/PowerBI-Time-Intelligence-Calendar-WTD-YTD-LYTD-Week-Over-Week/m-p/1051626#M184

Hi Anonymous , 

I think this might be caused by weeknum, I find that you seem to re-define the week num, and today(5/20) should be in 21 week. You could refer to my sample for details.

Best Regards,
Zoe Zhi

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Hi,

Please share the calculation that you used for calcuting the rolling average