Apex Date format

function rescheduleEvent(event,dayDelta,minuteDelta,allDay)
{
    console.log(event);
    var addSeconds = ((dayDelta * 86400) + (minuteDelta * 3600 ) + minuteDelta) * 1000;

    var updateObject = new Object();
    updateObject.id = event.detailData.id;
    updateObject.start_date__c = toSFDate(new Date(parseInt(event.eventStartEpoch*1000+addSeconds,10)));
    updateObject.end_date__c = toSFDate(new Date(parseInt(event.eventEndEpoch*1000+addSeconds,10)));


    fullCalendarController.saveObject(updateObject, function(result, event)
    {
        if(event.status)
        {
            console.log(result);

            /*
            Error gets returned.

Visualforce Remoting Exception: Upsert failed. First exception on row 0 with id a06S0000003yxF8IAI; first error: INVALID_TYPE_ON_FIELD_IN_RECORD, Start Date: value not of required type: 2012-02-03T14:46:00Z: [Start_Date__c]

            */
        }
    }, {escape:true});
}

function toSFDate(dateObj)
{
    // string format is YYYY-MM-DDThh:mm:ssZ
    var dateStr = dateObj.getFullYear()+'-'+pad2(dateObj.getMonth()+1)+'-'+pad2(dateObj.getDate()) +'T'+pad2(dateObj.getHours())+':'+pad2(dateObj.getMinutes())+':'+pad2(dateObj.getSeconds())+'Z';
    return dateStr;
}

function pad2(number)
{
     return (number < 10 ? '0' : '') + number
}