Calculating Durations between Dates
Use SUBDUR to calculate a duration by subtracting two dates, times, or timestamps. The result of the calculation is in whole units, and any rounding is done downwards. The calculation of durations includes microseconds.
Example
A duration of 59 minutes requested in hours will result in 0 hours.
A duration is 374 days requested in years yields 1 complete year because there are 1.02 years in 374 days.
If adjustment takes place on a date-time addition or subtraction, then a subsequent calculation will most likely result in a different duration than the one original one added or subtracted. This is because the subsequent duration will no longer contain a complete unit, and rounding down will yield one unit less than expected.