implementation date; date of execution
Refers to the scheduled date on which a plan, event, or measure is to be carried out. Common in official and business contexts.
The implementation date for the new system is the 1st of next month.
The date of the event has been changed.
日程 is a broader term for 'schedule' or 'itinerary', whereas 実施日 pinpoints the exact date of execution.
Compound of 実施 (implementation) + 日 (day).