Answer
A few things worth planning around: calendar generation should be run when few or no users are actively using the system, since it can cause performance impact, and generation time increases the further out the calendar is extended. As standard functionality, generating/regenerating a calendar recalculates each order line's Planned Receipt Date from its Planned Delivery Date plus the relevant lead-time components — if the recalculated date differs from what's currently saved, the system updates it automatically. Notably, these regeneration-triggered updates are deliberately NOT recorded in History Log (unlike a manual edit to the same field, which is logged), specifically because a single calendar regeneration can trigger a very large number of updates across the system and logging all of them would itself hurt performance. For example, making a specific date a new holiday causes any deliveries scheduled for that day to automatically shift to the next working day during the next calendar regeneration — existing open orders affected by such a shift may still need manual review/confirmation afterward, depending on business priorities.