Pls open the file koolreport/inputs/DateRangePicker.tpl.php and replace the following lines:

<div id="<?php echo $this->name; ?>" class="date-range-picker form-control">
    <input id="<?php echo $this->name; ?>_start" name="<?php echo $this->name; ?>[]" type="hidden" />
    <input id="<?php echo $this->name; ?>_end" name="<?php echo $this->name; ?>[]" type="hidden" />
    <div style="position:relative;">
        <i class="drp-icon <?php echo $this->icon; ?>"></i>
        <span></span>
        <b class="drp-caret <?php echo $this->caret; ?>"></b>   
    </div>
</div>

with this one:

<input id="<?php echo $this->name; ?>" name="<?php echo $this->name; ?>" class="date-range-picker form-control" />

But remember that when changing this the report's daterangepicker parameter would be a string in the format of {startDate} - {endDate} instead of an array of [{startDate}, {endDate}]. You would have to manually convert the range to start date and end date.

We will consider adding this as a template for daterangepicker so that users have more than one choice of UI. Rgds,