When you have a datepicker as input, there are two ways:

1-Put the datepicker inside the blade view of Laravel, on upon receiving values posted, you sent value to report to display chart. So you will send the parameters to report like this:

$report = new MyReport(array(
    "date"=>$myDate, // $myDate is from your datepicker posted back.
));
$report->run();

2-Use the datepicker inside the report itself, then you can use the datepicker from inputs package. Please follow the inputs guidance. In this way, the datepicker will bind its value to the report's parameter. So you can init your report at normal:

$report = MyReport;
$report->run()->render();

In this way, you do not need to insert date parameters to the report, the report will renders the datepicker and then when user selects a date to submit, the report will receive "date" parameter through $this->params["date"].