The M3TPROC program computes time-aggregation for selected variables from time-stepped CMAQ files of types: BOUNDARY , CUSTOM , or GRIDDED. For each output time step and for each selected variable, the program writes the selected aggregate value of that variable to the output file, optionally renaming it in the process. For example, the program allows the user to construct a file of daily gridded 08:00-16:00 average ozone values derived from a standard MAQSIP output concentration file.