A method, apparatus, and computer instructions for managing a set of virtual clocks in a data processing system with multiple partitions. A "set-time-of-day" command is used in connection with each virtual clock to define a basis for its local date/time state via the following elements: (1) a partition peculiar time base reference value, and (2) a partition peculiar time offset reference value which corresponds to the state of an elapsed time counter at the point in time when the time base reference value is established. The partition time base reference and offset reference values are stored in memory. When executing a "get-time-of-day" command, these are retrieved along with the current state of the elapsed time counter facility to compute the current date/time state of the virtual clock for the partition.