According to your documentation http://developers.marketo.com/documentation/rest/get-lead-by-id/ leads createdAt and updatedAt timestamps should contain timezone information: "updatedAt":"2013-11-21T11:47:30-08:00".
Unfortunately right now this API call returns timestamps without timezone: updatedAt=2015-05-05 04:51:58. What is even worse the timestamp is a local marketo server time, not UTC. Would it be possible to fix this? Knowing exactly when lead was created and updated is crucial for us.