Calendar plugin suggestions

Does anyone of you know about a calendar plugin I can use for my website?

It needs to have some features:
*You should be able to set events and people should be able to view them without being registered
*Preferably people should be able to register for the events, but that is not necessary.
*It should have a way to be displayed like a proper calendar, with dates and you can switch month.
*Preferably people can view the event details in a popup window when they click on the desired date.

I hope you have some suggestions :slight_smile: