a computer - implemented method of recording the times of events related to the medical care delivered to patient , and for integrating those times to provide a patient history , including recording a first time of occurrence of a first event , recording first clock information characterizing a first time source from which the first time of occurrence was obtained , recording a second time of occurrence of a second event , recording second clock information characterizing a second time source from which the second time of occurrence was obtained , wherein the first time source and the second time source are independent of one another and not synchronized with one another , transferring recorded data so that the first time of occurrence , first clock information , second time of occurrence , and second clock information are accessible at a computer ; and producing a patient history using at least the first and second times of occurrence .