Entity viewer - some timestamps not displayed properly

From the linked issue, in the entity viewer, some timestamps are displaying using a different date format to the others.
E.g. normal timestamps are formatted d/MMM/yyyy h:mm:ss, whereas the incorrect ones are using a default format - yyyy-MM-ddThh:mm:ssZ.

The timestamps that appear to be failing are DateTime.MaxValue.

Suspected error with the class EntitySerializer.