Hi all, I am so close to finishing this process automation badge but am stuck in one area in Step 7.

I've built out my process builder as follows





And my date formula as follows
 

Case(MOD(Date__c-DATE(1900,1,7),7),0,"Sunday",1,"Monday",2,"Tuesday",3,"Wednesday",4,"Thursday",5, "Friday",6,"Saturday", "")

 

Challenge Not yet complete... here's what's wrong:  The Robot Setup Day of the Week formula does not seem to be working properly. The Day of the Week should not fall on Saturday or Sunday. 

It works nicely but doesn't seem to pass, what could be up.
 

Hi,

Can someone please explain me how the below formula works(Not sure why they have particulary used 1900-1-7  and how the case function works ).

Validates that the value of a custom date field is a weekday (not Saturday or Sunday).
Formula:  CASE(MOD( My_Date__c - DATE(1900, 1, 7), 7), 0, 0, 6, 0, 1) = 0
Error Message:    Date must be a weekday.
Error Location:    My Date