Time management is a feature essential to office information systems. in the OIS environment, in addition to a static definition of time attributes attached to data, a more complete definition is needed, to handle both static and transition times and representation of temporal relationships the TSOS model, an extension of the SOS model for office description, contains a time model suitable for both of these requirement in addition the TSOS time model allows the representation of calendar times at different levels of abstraction and contains a precise definition of temporal and logical functions on time another main goal of the TSOS time model is to allow a flexible representation of temporal conditions for triggering and control rules in the office environment, so that an intelligent rule invocation is possible.