Ok well one will fix ProfStef one day, probably before the Pharo 3.0 release.
To insert this code in your image and finish ProfStef, open the class browser (right click on the background, then class browser is the first context menu item), then right-click on the packages (left list), click on 'find class...', write 'Object' or 'ProfStef', press enter, then add a method with exactly this code (copy and past it):
executeMethod: method
� � ^ self withArgs: #( ) executeMethod: method
Then ProfStef should work. Updating ProfStef was in the TODO list for Pharo 2 summer release, but I guess one forgot this method.�
For Time now, you have:
Time now printString �===>>> print in 12h mode
Time now print24 �===>>> print in 24h mode
The object is the same, just the printing method is different.
By the way, a quick trick, when you look for senders or implementors or a message, write the selector anywhere, highlight it with your mouse, then right-click on it, click 'extended search...', then click 'senders of it ...' or 'implementors of it ...' so you can know directly who implements/sends this message without looking into all the class in the class browser. It helps a lot understanding code.
Pharo by example is good with Pharo 1.4. More recent version of Pharo may be a little different from what is in the book, however most of it should be very similar. The new book, Deep into Pharo is up to date with Pharo 3.0 but covers only advanced aspects of Pharo.
Enjoy working with Pharo :)