Thunderbird Calendar aka the Lightning add-on - Quo vadis?

Richard LEGER richard.leger at
Thu Aug 1 09:22:07 UTC 2019

 Date: Thu, 1 Aug 2019 00:19:06 +0200

> From: J?rg Knobloch <jorgk at>
> To: "tb-planning at" <tb-planning at>
> Subject: Thunderbird Calendar aka the Lightning add-on - Quo vadis?
> Message-ID: <4b897f58-fec6-a5f8-76db-5b9ca13c697a at>

Hi lovers of Thunderbird and calendaring,
> have you ever asked yourself where one of the "productivity components",
> the Thunderbird Calendar is going?
> Long-standing bugs that have been astonishing the community like...

Hi Jorg,

Thank you for your initiative. As an end-user and very small contributor
having interest in Thunderbird calendar feature, answers to your questions
about it would be quite welcome.

I believe end-users (at least those I know who are relying on calendar
feature about 20+ users) share expectations that calendaring would have
become a performant and reliable core feature of TB by now :-) It would be
good to know plan and timetable on how on-going issues will be fixed in the

If I may add one more item of utmost importance to your long list of
bugs... surprisingly missed:

Lightning CalDAV performance issues [0] that have been plaguing Thunderbird
for years...
- 100mn+ to load one calDAV calendar with (~4000 items) in TB 60.8 [1]
- ~47mn to load the same calendar in 68.0b [1]

Major performance issues that cause users to leave a product should be
considered as major code flaws that need fixing urgently on par with
correctness fixes, and prioritized as such. Too often this is not the
case.The fact that performance issues were not even mentioned in your list
of calendar issues is a clear example and quite surprising :-)


To be fair, a fair amount of work has been done on the calendaring system
to keep it up and going (thank you to all those that may that happens
daily!) but it seems from my understanding that time and resources is the
root cause for bugs not being fixed for so long...

So another questions that may raise is: "what is the plan" to fix the
"time&resource" issue which in itself is a primary bug to fix?

Looking forward to the answers of your questions and have calendar feature
become a reliable and performant core feature of Thunderbird.

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