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We might want to schedule against the intended start time of an activity, not just the time it finishes. We might want to schedule against the start of an activity if and only if that activity is finished.
Cron schedules and the absolute time window complicated the v1 scheduler. The absolute time window should be removed (there are better ways to start/end a study), and the cron scheduler remains unuseful and can also probably be removed. We could possibly keep it if we can think of a good way to convert its timestamps to LocalDateTime instances. Maybe?