The calendar now reads all collection events, not just the next one.
This required quite brutal code refactoring of the sensor integration, as it has to be able to find a date from any generic data (including re-calculating groups). And the integration is now creating a structure of all entities so that it can query them at any time. So I will leave it for a while in beta to make sure it works. Thanks to @hasenbolle for the suggestion - I thought about that initially but decided to be lazy, this gave me a kick.
Anyhow, two other changes. @hasenbolle contributed a new attribute holiday_in_week_move, that automatically moves the collection to the next day if the collection comes to holiday.
And I changed (added) the device class, which might help with the translation issues reported in #142