>
> myCalendarTime + 3 days
> myCalendarTime - 3 hours
> myCalendarTime roundTo: 30 minutes
>

Hi Chris,

I added some of your ideas obove to my classes.

I decided to use nanosecond precision for both Duration and DateAndTime to 
forgoe ever having to create another class. It does use more storage (2 
words insted of one) but I have ideas on how to optimise this if required.

Regrettably my Duration classes clash with your MaDuration.

Cheers

Brent