Since NSDate represents "a single point in time, independent of any particular calendrical system or time zone", is it OK to make direct calculations with seconds given by its methods like
- (nullable NSDate *)dateByAddingComponents:(NSDateComponents *)comps toDate:(NSDate *)date options:(NSCalendarOptions)opts
Adding may make less sense, but subtracting does make sense if you want to find the difference in time between two dates.
What you want to note, however, is that you should only go for the seconds, minutes, hours, days, weeks difference from your subtraction
But to find the difference in months and years, you will want to use the
NSDate API. Months and years are not constant
Likewise with adding dates, if you want to add seconds, minutes, hours, days, weeks. Those are constant and easy to add. But Months and Years will trip you up