Gridview date separator

Hello everyone!

I’m a very-very beginner and have some trouble with customizing gridview. I have this code in view-file:

<?= GridView::widget([

	'dataProvider' => $dataProvider,

	'columns' => [

		['attribute' => 'id', 'label' => 'ID'],

		['attribute' => 'timestamp', 'label' => 'Date'],

		['attribute' => 'lat', 'label' => 'Ln'],

		['attribute' => 'lon', 'label' => 'Lg'],

		['attribute' => 't_onboard', 'label' => 't* onBoard'],

		['attribute' => 't_gsm', 'label' => 't* tModem'],

		['attribute' => 'serialno', 'label' => 'Number'],

		['attribute' => 'ver_fw', 'label' => 'ver'],

		['attribute' => 'balance', 'label' => 'code'],

		['attribute' => 'modemmodel', 'label' => 'model'],

		['attribute' => 'rssi', 'label' => 'RSSI'],


]); ?>

$dataProvider is just SqlDataProvider instance.

After render it looks like so: (sorry, as a newbie I can not post active links or embedded pics)

What I need is a date separation. If previous row contain date of 1st March and next row contain date of 2nd March I want to insert new row between them. Like so:

I just don’t know how to do that. I guess I need to make my own inheritor and override something, but I don’t know what exactly. Can anyone help me please?