Here is invoice created with "Add charge" and "Charge immediately". It has date 1/1/70 and "Paid" comment though it's in Due payment status.
Here is screen short form our test site:
Sorry about the delay in responding to this. I'll ask our Engineering team to look into this. We'll reach out to you in case we need more clarification
<?php echo date('d-M-y', $invoice->date) ?>
2) Printing paying date: https://github.com/chargebee/customer-portal-php/blob/master/portal/invoiceTable.php#L46
Should print only if status is payed:
<?php if ($invoice->status == "paid") echo 'Paid on '. date('d-M-y', $invoice->date) ?>
Thanks for the update Vlad. Our Engineering team has informed us that they'll update the code soon.