SUBDUR operation code is used to perform arithmetic difference of duration in factor-2 from DATE, TIME, or TIMESTAMP value in factor-1. The result is placed in result field.
Valid duration codes are *YEARS, *MONTHS, *DAYS, *HOURS, *MINUTES, *SECONDS, *MSECONDS.
Abbreviated duration codes can also be used: *Y, *M, *D, *H, *MN, *S, *MS.
