[Kassa Compleet] What is the right format of a customer's birth date in a «POST /v1/orders/» request?

The customer/birth_date property is absent in the JSON Schema of a «POST /v1/orders/» request, but is passed by the official extension for Magento 1.x.

So, it looks like the right format is ISO 8601 / RFC 3339.

An example: 1982-07-08 00:00:00.

The official Kassa Compleet extension for Magento 1.x uses the magic Mage_Sales_Model_Order::getCustomerDob() method:

It returns a value in a format like in my example above.