Why is date_created field is ignored for Contact creation via API?
Mike,

Unfortunately you can't set created_date in create api of Contact since there is a trigger which will over-ride your created_date value

DELIMITER $$
CREATE TRIGGER `civicrm_contact_before_insert` BEFORE INSERT ON `civicrm_contact` FOR EACH ROW BEGIN  
SET NEW.created_date = CURRENT_TIMESTAMP;
 END
$$
DELIMITER ;


Either you can delete this trigger or update the contact using same api by passing contact id to set created_date after its been created

https://somewhere.com/sites/all/modules/civicrm/extern/rest.php?entity=Contact&amp;action=create&amp;api_key=userkey&amp;key=sitekey&amp;json={"contact_type":"Individual","last_name":"test","first_name":"Peteww"}

https://somewhere.com/sites/all/modules/civicrm/extern/rest.php?entity=Contact&amp;action=create&amp;api_key=userkey&amp;key=sitekey&amp;json={"id":"288","created_date":"2018-01-01"}


Thanks