There's a saying that 'all good things come to an end' and when someone leaves, it may be the end of a great working relationship...however for your cowoker, the benefits of moving outweigh the urge to stay. You may easily ask "When's your final day?"
"Oh. I'm leaving on Friday."
"We;ll be sorry to see you go!"
"I know, but we'll keep in touch, right?"
"Sure thing!"
'all good things come to an end' ；という誰かが退職する時の表現があります。職場仲間であった人との関係を惜しむ言い方です。しかし、そこにいるよりは退社した方が良いと判断したんでしょうね。単純に"When's your final day?"と尋ねても良いでしょう。
"Oh. I'm leaving on Friday." 金曜日に出ていく予定だよ。
"We;ll be sorry to see you go!" 退社するなんて寂しいな。
"I know, but we'll keep in touch, right?"ああそうだね。連絡はとりあおうよ。
"Sure thing!" もちろんさ。
I know you have handed in your notice...But what date will you leave?
A "leaving date" is probably going to be a month after we "hand in our notice" to quit. We can expect a more accurate answer if we ask for the leaving date;-D "I know you have handed in your notice...But what date will you leave?"
A "leaving date"とは、退職届を出しておそらく一カ月後くらいになるでしょう。退職の日を聞いたら、正確な日をしりたいかもしれません。
"I know you have handed in your notice...But what date will you leave?"
退職届を出したのは知っているんだけど、何日に辞めるの？
日本 
アメリカ合衆国 
イギリス 
カナダ 
南アフリカ 
