When adding a recurrent event, it would be most practical to have the option to set it without end date (selectable).
Consider if you want to add Christmas as a holiday, then you want that to occur every year from now to ... well, to the end of time really (or until you remove it).
As it is now, you have to specify an end date regardless... not a good thing.

Additional feature suggestions that ought to be included to the Calendar;

1/
Option to switch between an single event to a recurring (and vice verse). And, of course, also Ranged events.
Today it seems that once an event is created, it stays that way (in regards to single/ranged/recurring) :(

2/
Possibility to 'copy' an already existing event to a new one (for further processing). Especially useful when you want to re-use an already made event, for the next time, might be repating holidays that have changing dates (yearly basis) or simply the monthly meeting, who knows?

3/
Support for colors in the 'Event title' field. Especially useful for e.g. 'red' holidays that is work free :)
Or any other events that one would like to single out for some reason...

Adding a snapshot that hopefully highlights the suggested additions/changes in a better way.

i kind of like some of those.