質問: I was reading a passage (from AIAIJ) and came across this sentence: > > ベティーは、日本でホームステイを**した時**、スリッパの使い方になれるまで、ずいぶん時間がかかった。 > > > I was wondering why した時 is used. To me, this gives me the nuance of "*After* Betty did her homestay..." rather than the (I think) correct reading of "When Betty was doing her homestay..." Is there a reason why this is preferred to using something like **している時**? The action that Betty does appears to take place *as* she is doing her homestay, not *after*, which would seem to not warrant the past tense preceding 時. Or perhaps there is a more crucial part of the sentence I misread? Regardless, I appreciate the help!
回答: 1. していた時 2. している時 3. した時 It depends on the related events were in a certain period of time or a moment. We choose to say していた時 and don't think other options in this case, because it has a certain period of time. However, した時 isn't too bad, we often say this in oral, and in your case I see no problem. Also, している時 is used when the event was **not too old in one's mind**. For example, A: 爪切り持ってきてくれた? B: 昨日、妹に貸した時に返してもらうのを忘れた A: どうして帽子かぶってないの? B: あっ、掃除をしている時、机の上に置いままにしてた Now back to your case, I think this follows almost the same tense in English but for sure we have many exceptions. 私がホームステイをしていた時、金閣寺はまだ修理中でした 私がホームステイをした時、はじめて納豆の匂いを嗅ぎました 私がホームステイをした時、日本人はトイレでスリッパを履き替えるのを知りました 私がホームステイをしている時、スカイツリーが完成しました All above are appropriate and interchangeable except the combination of this. 私がホームステイをした時、スカイツリーが完成しました This has a nuance of 'the Skytree has been built on the day I started my home-stay'. It sounds weird but the Skytree construction doesn't depend on your travel. 私がホームステイをした時、みんなに正しいパンケーキの焼き方を広めました 'While I was doing my home-stay, I have introduced the proper way of making pancakes.' If you are the pancake ambassador and this sentence makes a very good sense in Japanese minds. オランダ人がはじめて長崎に来た時、日本人は髪の毛が赤い人もいるということを知りました The same reason, this sentence is correct. And している時 orしていた時 doesn't fit.