A system that manages dynamic time zone definition updates can access stored time zone definitions and receive a subscription request from an application. The system can receive new time zone definitions and, while the application is being executed, update the stored time zone definitions to include the new time zone definitions. The system can then send a notification to the application that the stored time zone definitions have been updated, and the notification can cause the application to resolve impacts, if any, of the time zone definition update while the application continues to be executed.