Roadmap assigning dates to sprints with no dates

[rolfrussell]

I have a sprint (On Deck) with no dates.  In the roadmap we have turned on the feature that rolls up dates from sprints.  Stories in On Deck don't have any dates.  Not does the sprint have dates.  But in the roadmap the stories show dates based on the position of the sprint in the backlog (it is last just above "Backlog").  In other words the roadmap seems to be guessing dates for the sprint and using those dates for the stories.

How do I stop the roadmap from guessing dates for these stories and instead just leave them blank?

[Martin Bild]

We also have this behavior. Is there a solution or work around?

[veronie]

Same problem here. With this behavior, the automatic deduction of dates based on sprints is useless for us. 

We use sprints in the board to sort the backlog into categories. These sprints typically do not have dates, but the timeline deduces some seemingly random time spans for these sprints.