Hill Charts ask people to place a task on a hill shape based on how much uncertainty is left, not how many days remain, which is a genuinely different way of thinking about progress than a timeline bar. The Schedule tool handles dates and milestones in a simple calendar view, but it doesn't link tasks together with dependencies the way a Gantt chart does.
This isn't a missing feature so much as a stated position: Basecamp's maker, 37signals, has been public about not wanting to build a Gantt view that implies a precision most project schedules don't actually have.