librenms-librenms/html/includes/print-date-selector.inc.php

<?php

echo "
    <center>
        <form class='form-inline' id='customrange'>
        <input type=hidden id='selfaction' value='" . $_SERVER['REQUEST_URI'] . "'>
";

echo '
        <div class="form-group">
        <label for="dtpickerfrom">From</label>
        <input type="text" class="form-control" id="dtpickerfrom" maxlength="16" value="' . $graph_array['from'] . '" data-date-format="YYYY-MM-DD HH:mm">
        </div>
        <div class="form-group">
        <label for="dtpickerto">To</label>
        <input type="text" class="form-control" id="dtpickerto" maxlength=16 value="' . $graph_array['to'] . '" data-date-format="YYYY-MM-DD HH:mm">
        </div>
        <input type="submit" class="btn btn-default" id="submit" value="Update" onclick="javascript:submitCustomRange(this.form);">
        </form>
        <script type="text/javascript">
    $(function () {
        var strfrom = new Date($("#dtpickerfrom").val()*1000);
        $("#dtpickerfrom").val(strfrom.getFullYear()+"-"+
            ("0"+(strfrom.getMonth()+1)).slice(-2)+"-"+
            ("0"+strfrom.getDate()).slice(-2)+" "+
            ("0"+strfrom.getHours()).slice(-2)+":"+
            ("0"+strfrom.getMinutes()).slice(-2)
        );
        var strto = new Date($("#dtpickerto").val()*1000);
        $("#dtpickerto").val(strto.getFullYear()+"-"+
            ("0"+(strto.getMonth()+1)).slice(-2)+"-"+
            ("0"+strto.getDate()).slice(-2)+" "+
            ("0"+strto.getHours()).slice(-2)+":"+
            ("0"+strto.getMinutes()).slice(-2)
        );
        $("#dtpickerfrom").datetimepicker({useCurrent: true, sideBySide: true, useStrict: false});
        $("#dtpickerto").datetimepicker({useCurrent: true, sideBySide: true, useStrict: false});
});
    </script></center>
';