Lightning Calendar
Organize your schedule and events in a calendar fully integrated with Thunderbird or Seamonkey email.
What is Lightning Calendar?
Organize your schedule and life’s important events in a calendar that’s fully integrated with your Thunderbird or Seamonkey email. Manage multiple calendars, create your daily to do list, invite friends to events, and subscribe to public calendars.
Lightning brings the 
Sunbird (Sunbird is discontinued) calendar to the popular email client, 
Thunderbird and the 
SeaMonkey internet application suite. Since its an extension, Lightning is tightly integrated with Thunderbird or SeaMonkey, allowing it to easily perform email-related calendaring tasks.
Lightning Calendar Screenshots
Lightning Calendar Features
Lightning Calendar information
Supported Languages
- English
Comments and Reviews
Tags
- Calendar
- thunderbird-extension
- seamonkey-extension
- calendaring-software
- event-calendar
- calendaring
- calendar-events
- Task Management
Category
Office & ProductivityRecent user activities on Lightning Calendar
Maoholguin added Lightning Calendar as alternative(s) to Daybridge
RemovedUser added Lightning Calendar as alternative(s) to Skiff Calendar- RemovedUser added Calendar Integration as a feature to Lightning CalendarRe
We need Android version!!
Lightning by Mozilla Calendar Project is an add-on for Thunderbird, but I am looking for a standalone calendar.
https://addons.thunderbird.net/en-US/thunderbird/addon/lightning/
Can anyone recommend a standalone calendar application?
Reply written ago
Almost perfect, but sometimes annoying.
Pros:
Cons:
Price-wise (free) and feature-wise, Lightning is great. It's got every feature you could think of. Unfortunately, there are just enough bugs in it to be annoying.
The biggest problem is sync errors. If you delete a recurring entry in Lightning, it can (not always, but sometimes) delete the event, but not update it online. Then it's downloaded again. It's not deleted but it's flagged as deleted, so it's duplicated, then re-duplicated, then re-re-duplicated, etc. I've seen a calendar entry with 300+ duplicates. If you delete the calendar in Lightning before it syncs and screws up the web calendar too, you can just recreate it and you're fine. But it's an issue.
If you flag web calendars are read-only in Lightning and only update them online, there's no problem.
The other issue is reminders. If you set a reminder, sometimes you'll get the popup, dismiss it, get it again, dismiss it again, get it again, etc. Sometimes shutting down Thunderbird is enough to stop it, other times it's not. In those cases, the only option is to change the calendar entry to not notify you, otherwise, you'll get infinite reminders that cannot be dismissed. That's been reported as far back as 2011, and there's still no fix. It's intermittent, but it's a serious problem.
Lightning is a good calendar app, better than the Windows 10 native calendar. But the problems above prevent it from being a great app, unfortunately.
Every time Thunderbird updates, this calendar tab vanishes.
It cannot be found under "View" but SEEMS to be there as 'Calendar' and 'Tasks' are there but grayed out.
It gets me every time - you have to select ""Events and Tasks" and then the tab comes back again! An incredibly silly design! The forums are full of people saying "Thunderbird updated and my calendar is gone" and they are offered a detailed multip-step way of editing config files and stuff. You don't need to do any of that, just ignore the fact it's grayed out and not visible and just click the Events and Tasks button anyway, then your calendar comes back. Ridiculous, but does work.
EssentialPIM has calendar, to do list, notes, contacts, email and password list.
Thunderbird/SeaMonkey + Lightning have all these features, minus notes and password list. These two missing features can be supplemented by other open source software, such as Cherrytree and Password Gorilla.
So, I believe Thunderbird/SeaMonkey + Lightning are the open source softwares that have the feature set that comes closer to EssentialPIM.
Runs perfectly in Thunderbird 3.0.1 with Google Calendar Provider. A highly recommended add-on for Thunderbird users.