The deadline for Unique Device Identifier (UDI) implementation for medical devices is September 24, 2014. This deadline applies to Class III (including class III I/LS/LS) devices licensed under the Public Health Service (PHS) Act, and Humanitarian Use Devices.
In a recently-published 14-page document, FDA answered FAQs regarding UDIs and provided information on critical dates, label formatting and technology requirements, direct marking criteria and the Global Unique Device Identifier Database (GUDID), as well as exceptions, alternatives and exemptions to UDI requirements.
Source: Unique Device Identifier System: Frequently Asked Questions, Vol. 1