Mixing posts with calendar evetns

Hi,

I would like to have a category for upcoming events, but since some of them have an exact date, and some don’t, it would be great if there was a way to add a date in a custom field or somewhere else, so that the ones that have a date can be viewed via a calendar widget.

It may sound confusing but the point is this – I want all the events in one place, but since all of them don’t follow a certain criteria – as in having any date associated with them, I have to find a way to connect the events category posts with a calendar plugin.

How could I do this?