Date formats for Prompts different in DS1.6 to DS1.5

I have a set of queries to UNXs in a dashboard that worked fine in 1.5 sending date prompts as yyyy-mm-dd

Since upgrading to 1.6 these no longer work.

I have tried everything I can think of.

Has the required format changed?

Below is the code I am using.

Global Script - ConvertDate

// convert the dates in the date components from yyyymmdd to yyyy-mm-dd

//take the values in the date components and put into a temporary variable
var datefrom = DATEFIELD_1.getDate();

//split the strings down into the year month and day parts
var fromyear = Convert.subString(datefrom,2,4);
var frommonth = Convert.subString(datefrom,4,6);
var fromday = Convert.subString(datefrom,6);

//populate the global date variables with the new format date strings
xdate1 = "20"+fromyear+"-"+frommonth+"-"+fromday;

Text1 - OnClick

DS_2.setVariableValueExt("psDate1",xdate1);

DS_2.loadDataSource();