now for real

app/controllers/assignments_controller.rb

@@ -70,8 +70,8 @@ class AssignmentsController < ApplicationController
           other_users = other_users - [ @user.name ]
 
           event = Icalendar::Event.new
-          event.dtstart = Icalendar::Values::DateTime.new(session.starts_at, tzid: session.starts_at.zone)
-          event.dtend = Icalendar::Values::DateTime.new(session.ends_at, tzid: session.ends_at.zone)
+          event.dtstart = Icalendar::Values::DateTime.new(session.starts_at, tzid: session.starts_at.time_zone.tzinfo.name)
+          event.dtend = Icalendar::Values::DateTime.new(session.ends_at, tzid: session.ends_at.time_zone.tzinfo.name)
           event.summary = [session.title, session.stage.name].join(' @ ')
           event.description = other_users.join(', ') + "\n\n" + helpers.strip_tags(session.description)
           event.location = [session.stage.name, session.conference.name].join(' @ ')