You can easily set date in invoice using setInvoiceDate function. By default, default date is set in config. You can directly change default date in config also. You can also set date using the generic function setInvoiceData for changing data. Apart from setting date here, you can also set "defaultDateVal" = "current_date" in setting file and it will automatically pick the current date as per datetime zone.
$xinvoice = new Xinvoice(); // You can set invoice date using this function or can change directly in config file. $xinvoice->setInvoiceDate("01/04/2018"); echo $xinvoice->render();