The archived wiki mentioned in #9 hints that one may be able to load GNOME Planner XML data; the GNOME planner page has a section on 3rd party tools that says one may use an xslt-script for this.
The latest archived copy I was able to find was here: https://web.archive.org/web/20130529111038/http://simile.mit.edu/wiki/Timeline/Planner
The archived wiki mentioned in #9 hints that one may be able to load GNOME Planner XML data; the GNOME planner page has a section on 3rd party tools that says one may use an xslt-script for this.
The latest archived copy I was able to find was here: https://web.archive.org/web/20130529111038/http://simile.mit.edu/wiki/Timeline/Planner