The project started with a single extension for the Mozilla projects known as Mozilla Calendar.

Sunbird and Lightning are both free software, released under the Mozilla tri-license: the Mozilla Public License, the GNU General Public License and the GNU Lesser General Public License. This allows you to read and write to your calendar while offline and can also reduce network traffic.The Mozilla Calendar Project was the name for the Mozilla project that led to the development of Sunbird calendar application and the Lightning integrated calendar. Offline Support: If checked, your remote calendar is synchronized on your hard disk.Show Reminders: This enables/disables the reminders portion of the calendar.(Can also be made read-only by clicking on the 'color' of the calendar in the calendar tab.) This is very nice for shared office calendars that you don't want to edit by accident. Read Only: If checked, this makes the calendar not editable by default.Refresh Calendar: This is how frequent Thunderbird will check for changes on the calendar details.E-Mail: This is the email address Thunderbird uses to send invitations for events.Do not edit this unless you know what you are doing.

Location: This is the location of your calendar.

Color: By clicking on the box next to the word Color, you can change the background of all your calendar events to something more pleasing to you than blue, like mauve, purple, or yellow.

Calendar Name: Here you can choose to change the name of your calendar, for example from Home to Private.

To change the preferences of a single calendar, either double-click on it or highlight the calendar you want to edit, then click the Edit menu from the top and select Calendar properties. This article describes how to change the preferences (name, color, location etc.) of a single calendar.

Mozilla thunderbird calendar