We use the word 時 to describe when something happens or happened
Sentence A 時、Sentence B. – When A, B.
(Time reference) (main event)
日本に行った時、富士山に登りました。
When I visited Japan, I climbed Mt. Fuji.
The sentence A always ends with a short form, either in the present tense or the past tense.
If A is current or yet to happen, use the present tense in A. If A has already taken place, use the past tense.
明日彼に会う時、この洋服を着ます。(not yet happened – present tense)
When I see him tomorrow, I will wear this clothes.
<(Main event) before (time reference) >
If, at the time the main event B takes place, A is current or is still “in the future”, use the present tense A.
日本に行く時、ビザを取りました。
(日本に行こうとした時）When I was going to Japan,
I had the visa issued when I was going to go to Japan.
* You haven’t gone to Japan yet. You get visa before you go to Japan.
Other example
寝る時、コンタクトレンズを取ります。
When (before) I go to sleep, I take out the contact lenses.
出かける時、鍵を閉めました。
When (before) I went out, I locked the door.
彼と会う時、おしゃれをします。 おしゃれー fashionable おしゃれする – dress up.
When (before) I see him, I dress up.
うちの柴犬の太郎はお散歩に行く時、うれしくて庭を走り回ります。
When (before) we go for a walk, our Shiba dog, Taro, runs around the yard.
< (Time reference) = (Main event) same time>
さびしい時、友達に電話します。
When I am lonely, I call up friends.
お腹が空いた時、バナナを食べます。
When I am hungry, I eat banana.
寒い時、頭が痛くなります。
When it’s cold, I get a headache.
* It happened same time.
<(Main event) after (time reference)>
中国に行った時、ウーロン茶を買います。
I will buy oolong tea when (after) I go to China.
中国に行った時、ウーロン茶を買いました。
I bought oolong tea when (after) I went to China.
* You already arrived in China, then, you buy oolong tea.
疲れた時、ゆっくりお風呂に入ります。
When I have gotten tired, I take a long bath.
(You git tired (A) and then, take a bath (B).)
宿題を忘れた時、泣きました。
When I had forgotten to bring the homework, I cried.
(You found out about the homework (A) and then cried.(B))
When (before) I go to NY I will buy a warm coat
ニューヨークに行く時、あったかいコートを買います。
When I dropped my meal plate, I cried.
食事のお皿を落とした時、私は泣きました。
When (after) I ran, I massage my legs.
走った時、私は足をマッサージします。
It’s important to understand the conversation flow, and know the meaning.