Is there a facility for writing a generator that generates the next value based on the previous? e.g., similar to iterate

Generators aren't meant to be aware of previously generated values. If this is part of a larger structure, you could describe that and there might be another way

The objective is to generate a seq of dates increasing over time separated by a bounded, random amount of time.

Trying to generate data that imitates what actual data will look like.

Generate the start date and the increments, and then fmap the result to get what you're describing