Using an add-on for Mozilla Thunderbird called Lightning, you can view events properly in Mozilla Thunderbird.

There are currently 2 Mozilla projects that let you do this, Sunbird and Lightning. I prefer Lightning because it integrates nicely with the email client.

You can view more information on the Mozilla Calendar Project.
Have you ever received those Events sent by Microsoft Outlook, and see them as raw text, like this:
Raw text:
BEGIN:VCALENDAR
PRODID:-//Microsoft Corporation//Outlook 11.0 MIMEDIR//EN
VERSION:2.0
METHOD:REQUEST
BEGIN:VEVENT

When you install the Lightning Add-On, you get a better view of the event.
You can also send events, and view your following events inside the thunderbird client.
This is how you see it once it’s installed: