process duration data are generated that are independent of a reference calendar date , by conversion of a given duration data set , comprised within a process description data set , in a converted duration data set , the given data set being first converted into an intermediary data set that is compliant to a data format specified in the international standard iso 8601 and includes the following consecutive fields : a first delimiter , a years value , a years value field identifier , a months value , a months value field identifier , a days value , a days value field identifier , a second delimiter , an hours value , an hours value field identifier , a minutes value , a minutes value field identifier , a seconds value , a seconds value field identifier . a target data set is first created with a first placeholder for a converted months value and a second placeholder for a converted seconds value , a first equation is solved by applying the years value and the month value as parameters to the equation ; a second equation is solved by applying the days value , the hours value , the minutes value and the seconds value as parameters to the equation . the first and the second placeholders are replaced with the converted months value and the converted seconds value respectively and the target data set is stored as the converted duration data set in the process description data set .