oca-workflow-process/odoo-bringout-oca-purchase-workflow-supplier_calendar/supplier_calendar/readme/USAGE.rst

When a picking is created from a purchase order of a supplier, the lead
time used to calculate the scheduled date is computed in natural days. At the
same time, when a purchase order is created due to a a procurement
evaluation, its order date is also computed considering the lead time in
natural days. THis module adds the possibility of expressing the lead time
of a vendor in his own calendar. This way, the order dates of purchase
orders and the scheduled dates of receipts will only take into account the
supplier working days.