Solution could be to use on_data_display event handler and on getting date value 01-01-1970, replace it with ''
Code would be something like following:

$e["on_data_display"] = array("filter_display", null, true);
$grid->set_events($e);

function filter_display($data)
{
foreach($data["params"] as &$d)
{
foreach($d as $k=>$v)
if ($d[$k] == "01-01-1970")
$d[$k] = "";
}
}

Hello,

I have a bit similar problem about null date from database that will display 01-01-1970 but it is after it has been export to excel file..how can I solve the problem?

Is it the same answer as above? where should I put the code?

Thank you..

Regards,
Ad

Yes, same will apply with export. Export uses on_data_display event.
Refer demos/editing/custom-events.php for reference.