My project is very long and the Gannt show only days, not week or month.
Idem as http://forum.plantuml.net/7637/change-gantt-scale-for-long-projects?show=7637#q7637
We have started to enhance gantt feature.
With last beta http://beta.plantuml.net/plantuml.jar and on the online server, you can now use
to change the resolution of a gantt.
This is really an early version, so any feedback is welcome
You can also use :
to split your diagram