dynamic datetimepicker issue

Question

This is a simple case of closure surprises. Just move the functionality to a method and call it from the loop passing it counter in each turn. Like so:

var myMethod = function myMethod (counter){
  var appendTxt = "<div style='display:none' class='divRow5 HideSchedule'><div class='divCellouter4'><div class='divCell2 rowwidth13 brdrStl4'><input name='NEW_STARTdatetime[]' class='dtpkr' type='textbox' readonly='readonly' id='NEW_STARTdatetime["+counter+"]' value='' autocomplete='off' size='10' /></div><div class='divCell2 rowwidth13  brdrSt14'><input name='NEW_ENDdatetime[]' readonly='readonly' autocomplete='off' class='dtpkr' type='textbox' id='NEW_ENDdatetime["+counter+"]' value='' size='10' /></div><div class='divCell2 rowwidth13  brdrSt14'><input name='NEW_START_TIME[]' type='textbox' class='tmpkr' id='NEW_START_TIME["+counter+"]' value='' size='10' /></div><div class='divCell2 rowwidth13  brdrSt14'><input name='NEW_END_TIME[]' type='textbox' class='tmpkr' id='NEW_END_TIME["+counter+"]' value='' size='10' /></div><div class='divCell2 rowwidth8   brdrSt14'><input type='checkbox' name='new_promo_chk[]' id='new_promo_chk["+counter+"]' class='checkbox regular-checkbox big-checkbox' checked /><label for='new_promo_chk["+counter+"]'></label></span> </div></div><div class='divCell2 handcursor'> <img class='del' src='images/delete.png' /></div></div>";
  $('[id$="NEW_STARTdatetime\\['+counter+'\\]"]').datetimepicker({
    // minDate:'-1970/01/02',
    format:'Y/m/d',                
    onShow:function( ct ){                                
    this.setOptions({
     maxDate:$('#NEW_ENDdatetime\\['+counter+'\\]').val()?$('#NEW_ENDdatetime\\['+counter+'\\]').val():false
    })
    },
    timepicker:false     
    });
  $('[id$="NEW_ENDdatetime\\['+counter+'\\]"]').datetimepicker({
    //minDate:'-1970/01/02',
    format:'Y/m/d',                
    onShow:function( ct ){
      console.log('#NEW_STARTdatetime\\['+counter+'\\]');
      console.log($('#NEW_STARTdatetime\\['+counter+'\\]').val());
      this.setOptions({
       minDate:$('#NEW_STARTdatetime\\['+counter+'\\]').val()?$('#NEW_STARTdatetime\\['+counter+'\\]').val():false
     })
    },
    timepicker:false          
  }); 
}

for(i=0;i<5;i++){
 myMethod(i);
}

Now for the explanation. The onshow will be activated asynchronously, most probably AFTER your loop has finished. Therefore it gets only last value of counter. By moving it into a method, you create a new scope each time you call it. Thus, the passed value is preserved.

PS: I didn't check for any syntax errors.