[Seaside] Timespan bug

[Steve Aldred]

Sorry for posting this here but I don't use Squeak itself and hence 
aren't on the main squeak list.

As a VW Seaside user I do use Squeak extensions. There is a bug in 
Timespan as shown below:

  (Year starting: (DateAndTime year: 2008 month: 1 day:1)) previous

The result should be 2007 but it returns 2006.

Year should implement previous the same as Month does.

cheers
Steve