Abstract: A method in a network entity associates a unique identifier with an event, for example a television program. The method comprises the steps of receiving an original time reference allocated to the event, for example an original start time for the event, and generating a first identifier (event_ID) to identify the event, wherein the first identifier is based on a set of first identifiers (event_IDs) that have a predetermined repetition period. The method further comprises the step of generating a second identifier (program_ID) to identify the event, wherein the second identifier is unique over time and based on a function of the first identifier and the original time reference allocated to the event. Various embodiments describe how changes to the original time reference can be made, yet still allow the unique event identifier to be determined.