I find that japanese is a weird language for its learners,especially for those who had learnd english before,because in english there are present tense and past tense.However,in japanese there are accomplished tense and unacomplished tense which look so strange if compared with english . For instance.   わたしは日本に行くとき、ラジオを買ました　.its english translation is ' when i go to japan, i bought a radio', so the english sentence have two different parts which use two unrealted different tenses and obviously logical wrong.   Please look at another example.  私は日本にいきたとき日本製のテレビを買える予定です. its english translation is 'when i went to japanse, i decide to buy a TV made in japan', and this sentence sounds also strange.