What is the difference between (non-past sentence)とき(past sentence) and (past sentence)とき(past sentence)?

4 comments

1. the first sentence would mean “when I was going to Osaka, I went by airplane”. That’s the difference

2. 大阪へ行ったとき should be understood as “was in Osaka”, and 大阪へ行くとき should be understood as “on my road to Osaka”.

   Generally Japanese uses 2 time systems at the same time. One is absolute and similar to English, in the meaning that past/future is said relatively to speech time. Like “I will meet my friend when I will go” (will with both actions). Another is when one verb is relative to another and this is such case, 行く can have finished and unfinished state at the moment of meeting.

   In simple words it allows people to say before/after just by using different tenses, like “I met before I went” and “I met after I went/came”.

3. Try translating them directly to English.

   大阪へ行く時 -> “go-to-Osaka time”, the time where you’re physically travelling there.
   大阪へ行った時 -> “went-to-Osaka time”, the time after arriving in Osaka.

   “At the go-to-Osaka time, I went by plane”. That is to say, *while* travelling, you were doing it by plane.

   “At the went-to-Osaka time, I met my friend”. That is to say, *after* physically moving there, you met your friend.

   I think the confusion might stem from the fact that “travelling to Osaka” in English also includes the time spent in the city and the journey back, but in Japanese 行く時 indicates only the time spent getting there, while 行った時 will indicate only the time *after* the physical travel. To be honest, the translations given by the textbook, while correct in English, are rather poorly chosen from a teaching standpoint.

   Perhaps better and still mostly natural-sounding translations would be “I went by airplane when I travelled to Osaka” and “I met my friend *after* I travelled to Osaka”, but even then you still run into the problem with how “travelled to Osaka” in English usually includes the entire stay in Osaka and the journey back, whereas in Japanese it only refers to the journey there.

   ___

   I saw a similar example somewhere else, which might be clearer because it talks about the same thing in both cases:

   中国へ行く時、お茶を買いました。
   中国へ行った時、お茶を買いました。

   The first one indicates that you buy the tea while you’re travelling to China (like in the airport or on board the plane). The second indicates that you buy it *after* having travelled to China (like in a shop in Shanghai).

4. Understand that the easiest way to understand tense in Japanese (and especially tense in dependent clauses), is to discard the English past present future tenses, and think of Japanese as just having a completed/not completed tense system.

   So the first sentence talks about not completed action compared to the main clause; and the second talks about complete action compared to the main clause.

   It is surpersingly productive in general to think of Japanese having only a completed/not completed tense in general, but it is almost completely required to think that way when working with the tense of the dependent clause compared to the tense of the main clause. (coming from English).

   Remember the -tara ending is following that rule as well, one thing completed, the next thing follows.