System administrator and project manager can preset ganttchart default month.
git clone https://github.com/aki360P/redmine_gantt_default_month.git bundle install rake redmine:plugins:migrate NAME=redmine_gantt_default_month RAILS_ENV=production
and then restart server
rake redmine:plugins:migrate NAME=redmine_gantt_default_month VERSION=0 RAILS_ENV=production
Please choose option to enable plugin with administrator plugin configration.
Don't forget to give permission to manager role.
Plugin permisiion is included in exisiting "project" module.
Project manager can overwrite specific setting as a project default.