Calendar and Date/Time
The 'NoiaButtons' add-on offers cartoonish toolbar button icons (known from Noia themes) for default theme and lightweight themes. Further more lite silver and dark versions of Noia themes are included.
Open Google Calendar Requires Restart
Adds the Google Calendar web interface in a new Thunderbird tab. Creating and viewing events works like in a browser (Firefox, Chrome, ...)
TbSync is a central user interface to manage cloud accounts and synchronize their contact, task and calendar information with Thunderbird.
Send Later Requires Restart
True "Send Later" functionality to schedule the time for sending an email.
AdvancedTasks Requires Restart
Thunderbirds Lightning Extension: Allows the use of Markdown in Task descriptions and renders them as HTML in the TaskView.
Show Calendar Week Requires Restart
Shows the calendar week Thunderbird/Lightning calendar's moth and multi-week view.
Todo.txt Requires Restart
Thunderbird extension for the Todo.txt application
This extension adds support for CalDAV & CardDAV accounts to the Thunderbird Sync manager "TbSync".
Add sync support for Exchange ActiveSync (EAS v2.5 & v14.0) accounts to TbSync
LCD Clock Requires Restart
displays a LCD Clock in your Toolbar
Gantt View Requires Restart
Gantt Chart view for Sunbird/Lightning
EDS Calendar Integration Requires Restart
Integrates calendars events with Gnome clock applet
Plugin may hang on Fedora.
As a workaround uninstall evolution-ews.
ReminderFox displays and manages lists of reminders and ToDo's. ReminderFox makes sure you remember all of your important dates via easy-to-use lists, alerts, and alarms, right in your browser without the need for a separate calendar program.
MultiBirthdaysReminder Requires Restart
This addon is now integrated into the new address book CardBook and thus it is no longer maintained
Reply Monitor Requires Restart
**This is NOT COMPATIBLE with Thunderbird 31 or newer versions**
Keep track of your emails and replies (Lightning is required).
Note: the name of this add-on has been changed to Reply Monitor because the previous name is a registered trademark.
Lightning Calendar Tabs Requires Restart
Displays tabs which allows quick navigation between time periods in Lightning calendar. All views of calendar are supported. Color of tab texts can be adjusted.
More Snooze Requires Restart
This add allow to customize the snooze delay when snooze popup appears (lightning required).
SanRockstar Requires Restart
StormCows Requires Restart
Allows two-way access between Remember The Milk and calendar events or todo items.
Macro Template is to replace mail templates with macros for date formatting.