Change column widths
<code php>
            [
                'attribute'=>'xxx',
                'contentOptions' => ['style' => 'width:10px; white-space: normal;'],
            ],
</code>
Modify time display
<code php>
                'attribute' =>'starttime',
                'format'=> 'time',
</code>
Pass thru html code
<code php>
                'attribute' => 'content',
                'format' => 'html', // or raw
</code>
