The new TB update from today enables and installs lightning by default. Bugreport: http://bugs.archlinux.org/task/17510?project=1&pagenum=1 This is a bad idea, because some people don´t want it. Mozilla doesn´t recommend to set the calendar flag on building... Another point is, that the builtin calendar extension is not localized. So, on non-english systems people have a "language mix" in TB... -- Regards Juergen