noun
departure date; day of departure
Refers to the scheduled date on which a journey, flight, or trip begins.
出発日は来週の月曜日です。
The departure date is next Monday.
航空券には出発日が書いてあります。
The departure date is written on the plane ticket.
到着日 means 'arrival date', the counterpart to 出発日.
Compound of 出発 (departure) + 日 (day). The reading しゅっぱつび follows standard rendaku voicing of ひ to び.