Add a new logbook.set_datetime_factory() API, allowing the option of using datetime.now() instead of utcnow() if the user prefers time stamps in local time zone instead of UTC
Indent with spaces, not tabs.
Add a unit test for the new logbook.set_datetime_factory() API
Documentation for set_datetime_factory
set_datetime_factory -> set_datetime_format, as suggested by brainstorm
Merge pull request #74 from gjcarneiro/master

Simple change to allow local timezone time stamps to be displayed

Thanks for this patch @gjcarneiro, merging it in ;)