Eu quero validar 2 entrada de dados no codeigniter, com as condições, se a data de término for maior que a data de início, aparecerá aviso [aviso de javascript ou algo assim] ou dados não podem ser inseridos

minha forma assim,

<h1><?php echo $title; ?></h1>
<form action="<?= base_url(); ?>index.php/admin/kalender/buat" method="post" enctype="multipart/form-data" name="form" id="form">
<?php
echo "<p><label for='IDKategori'>Tingkatan Pimpinan :</label><br/>";
echo form_dropdown('IDKategori', $kategori) . "</p>";

echo "<label for='ptitle'>Kegiatan / Lokasi :</label><br/>";
$data = array('class' => 'validate[required] text-input', 'name' => 'judul', 'id' => 'ptitle', 'size' => 80);
echo form_input($data);

echo "<p><label for='long'>Uraian Kegiatan / Keterangan / Catatan :</label><br/>";
$data = array('class' => 'validate[required] text-input', 'name' => 'konten', 'rows' => '13', 'cols' => '60', 'style' => 'width: 60%');
echo form_textarea($data) . "</p>";

echo "<p><label for='ptitle'>Waktu Mulai :</label><br/>";
$data = array('class' => 'validate[required] text-input', 'name' => 'TanggalMulai', 'id' => 'basic_example_1');
echo form_input($data) . "</p>";

echo "<p><label for='ptitle'>Waktu Akhir :</label><br/>";
$data = array('class' => 'validate[required] text-input', 'name' => 'TanggalAkhir', 'id' => 'basic_example_2');
echo form_input($data) . "</p>";

echo form_submit('submit', 'Tambah Even');
?>
&nbsp;&nbsp;<input type="button" value="Kembali" onClick="javascript: history.go(-1)" />

como validar na forma "Waktu Akhir & Waktu Mulai"?