Event Calendar – populated by posts

Hi,

I am searching a Calendar Plugin that can do the following —

The calendar would be populated by the posts — when creating a post, the author would have the ability to set the event time and dates. Upon publishing the post, the calendar would be updated with the event (not a calendar of posts). If the post was created and not event information was added — then the calendar would not change.

I want to have the ability to update posts only and change the calendar. Not create ‘events’ and a post…