Subclassed DateTime's from_object method, which was secretely deleting
the internal session variable. There is probably a more robust way to
do this, such as by "...implementing the utc_rd_values() method as the
from_object docs suggest.
Finished fixing the bug with time zone errors in editing an event.
The standard is everything going into the DB is in UTC. Timezones have to be
manually handled after being fetched.
Added a test for the new methods and for object construction.
Changed Calendar and Event Assets to use the new methods.
Interim checkin to get some debug help from Doug.