var Time1 = $('#TextBox_Startdate').val();
    var Clock1 = $('#clock1').find(":selected").text();
    var Time2 = $('#TextBox_Enddate').val();
    var Clock2 = $('#clock2').find(":selected").text();

    var convertDate1 = new Date(Time1);
    var zone1 = convertDate1.getTimezoneOffset() * -1 / 60;
    var convertDate2 = new Date(Time2);
    var zone2 = convertDate2.getTimezoneOffset() * -1 / 60;

    var datetime1 = Time1 + "T" + Clock1 + ":00+" + "0" + zone1;
    var datetime2 = Time2 + "T" + Clock2 + ":00+" + "0" + zone2;

"<And>" +
    "<Leq>" +
    "<FieldRef Name='datetimedata1' /><Value Type='DateTime' IncludeTimeValue='TRUE'>" + datetime1 + "</Value>" +
    "</Leq>" +
    "<Gt>" +
    "<FieldRef Name='datetimedata2' /><Value Type='DateTime' IncludeTimeValue='TRUE'>" + datetime2 + "</Value>" +
    "</Gt>" +
    "</And>" +