This is the ValueSet that contains all the codes in MDC Time Synchronization Methods (http://hl7.org/fhir/uv/phd/ValueSet/MDCTimeSyncMethods) and MDC Time Synchronization Methods (http://hl7.org/fhir/uv/phd/ValueSet/MDCTimeSyncMethods). E.g. what you have to deal with if you get resources containing codes in either of them