Question: how to calculate days between two dates in tableau?
Answer: (DATEDIFF('day',[Day1],[Day2]) - (7-DATEPART('weekday',[Day1])) - ... 
(DATEDIFF('day',[Day1],[Day2]) Then we trim off days in the first partial week of the time frame. ... 
- (7-DATEPART('weekday',[Day1])) ... 
- DATEPART('weekday',[Day2]) ... 
+ MIN(5,(7-(DATEPART('weekday',[Day1])))) ... 
+ MIN(5,(DATEPART('weekday',[Day2])-1))