It's great to have a sprint feature in place with the newest release!
And it's also good to start creating sprints with a specified index such as "9" for instance.
However, when it comes to specify sprint dates, you have to stick with cycles you define in the settings such "2 weeks" or "4 weeks".
Of course it makes sense to have dates specified like that. I think ClickUp should always offer that cycles, however real life is not perfect and strict like that, even the calendar itself is not perfect considering some months have 5 weeks instead of 4 weeks. If you consider bank holidays too, sometimes it's not possible to stick to cycles. In exceptions like that, we should be able to specify specific dates for sprint timeline rather than cycles.
So, in addition to cycles offered by ClickUp for sprint timelines, there should be also an option where we can specify the dates, for instance, to extend that particular sprint to 5 weeks while you're working with "4 weeks" cycles