You are mixing JavaScript with FormCalc keywords.
EEEE- is a FormCalc keyword to get the Weekday.
In java Script, you can get the Weekdays in numbers.
So you have to write code to get the matching spelled out name for the weekday.
Try something like this..
var d=new Date();
var weekday=new Array(7);
weekday[0]="Sunday";
weekday[1]="Monday";
weekday[2]="Tuesday";
weekday[3]="Wednesday";
weekday[4]="Thursday";
weekday[5]="Friday";
weekday[6]="Saturday";
xfa.host.messageBox("Today is " + weekday[d.getDay()]);
Page1Header.ReportDay.rawValue = weekday[d.getDay()];
Thanks
Srini