prearranged date; scheduled date
Refers to a date that has been set in advance, often used in formal or business contexts.
The scheduled date for the meeting is next Friday.
予定日 is more common and general for 'scheduled day', while 予定期日 is more formal and often used in official or business settings.
Compound of 予定 (schedule, plan) and 期日 (fixed date, deadline).