Q: how to assign one event to two calendars

Pacone,

You will have to create two individual events.

Pacone,

The only other way that comes close to your desire is to use Copy/Paste, and assign the pasted event to the second calendar.

I use the Edit/Duplicate function to duplicate an event and then assign it to another calendar. Like the others, I have also not found a way around having 2 events (one per calendar).

Apple should really look into this.

TThis should be the next update for iPhone... very critical when dealing with multiple calendars.