Insert field type time

Hello,

I have a script where I received parameters, and next I insert in a table.  I need insert one parameters into a field type 'date', but to be insert I obtain an error.

"Javascript previus to RAD"

var number=vars.$file.number;
var start=vars.$downtime_start;

addTime(number, start);
function addTime(number, start) {
    var file = new SCFile("test");
    file.id = system.functions.get_uid();
    file.number = number;
    file.downtime_start=start;
     var rc = file.doInsert();
    if (rc == RC_SUCCESS) {
         return true;
    } else {
        return false;
    }
}

The error appareance is: "ERROR Cannot store a string into an object of type time at char 1".

How could I insert this data correctly?

Thank you in advance!!