In Legacy Workflow it was possible to create time based workflows based on trigger date/time. For example, send an alert to the assigned user when a not completed task is due in say 5 days. Another example, send an email to a user when the expected close date of an opportunity is a week away. Or even, send an escalated email to the assigned user and their manager that a task remains incomplete past its due date.
At present, this is not possible in SugarBPM - currently date based functionality is for either an elapsed time span or a specific date.
To successfully move away from Legacy workflow, it is probable that many users have simple workflows that carry out reminder and escalation processes based on these types of triggers and currently cannot develop these workflows in SugarBPM.