Why does the expected, required and promise dates differ between order, production and purchasing screens?

Hello Taylor, Thanks so much for your query. Production orders have a required date, which is different from an order date as a production order is needed before building an order. Promise dates have a different calculation logic. As a Prophet 21 customer we recommend you enter a case and provide a specific example. Our Application Support team would welcome the opportunity to work with you to help you better understand the logic and the process of a date calculation. We hope this helps and we look forward to hearing from you. Sincerely, The Epicor Team