To fix it, you need to use the radix argument for the parseInt method. Otherwise, any string input starting with a 0, will be treated as an octal base number.

Here is the fix:
function ConvertDateFromUTC(startDate){
// UTC time formatted string
//2009-03-25T09:30:00-00:00 // 1 2 //1234567890123456789012345

var year = parseInt(startDate.substr(0, 4),10);
var month = parseInt(startDate.substr(5, 2),10);
var day = parseInt(startDate.substr(8, 2),10);
var hour = parseInt(startDate.substr(11, 2),10);
var min = parseInt(startDate.substr(14, 2),10);

return new Date(year, month – 1, day);
}