Japanese Grammar

Saying 'When': 〜時 (toki)

〜時 (toki) means 'when' or 'at the time of'. The tricky part: the tense of the verb BEFORE toki tells you whether Action A is completed or not when Action B happens.

The Tense Puzzle of ~toki

~toki attaches to the Plain Form of verbs. However, whether you use the present or past form changes the meaning dramatically.

If Action A is NOT YET DONE when B happens → Use PRESENT form before toki.

If Action A IS ALREADY DONE when B happens → Use PAST form before toki.

This is independent of the overall sentence tense. You must think about the relationship between Action A and Action B.

Present vs Past Before 〜時

Present tense before 〜時 (A not yet done when B happens)
Rule
→Verb (present plain) + 時
B happens while A is still incomplete / about to happen
日本に行く時、地図を持って行く。
→Nihon ni iku toki, chizu o motte iku.
When I go to Japan, I take a map. (I haven't left yet)
寝る時、歯を磨く。
→Neru toki, ha o migaku.
When I sleep (before sleeping), I brush my teeth.
Past tense before 〜時 (A already done when B happens)
Rule
→Verb (past plain) + 時
B happens AFTER A is already completed
日本に着いた時、友達に電話した。
→Nihon ni tsuita toki, tomodachi ni denwa shita.
When I arrived in Japan, I called my friend. (Already arrived)
起きた時、もう８時だった。
→Okita toki, mou hachi-ji datta.
When I woke up, it was already 8 o'clock. (Already woken up)
With Adjectives and Nouns
I-Adjective + 時
→忙しい時、ご飯を食べない。
When I am busy, I don't eat. (忙しい - busy)
Na-Adjective + な + 時
→暇な時、映画を見る。
When I am free, I watch movies. (暇 - free)
Noun + の + 時
→子供の時、よく泳いだ。
When I was a child, I often swam.

Comparing present vs past before toki

財布を忘れた時、困った。
Saifu o wasureta toki, komatta.
When I forgot my wallet (past=already forgot), I was in trouble.
財布を忘れる時は、慌てる。
Saifu o wasureru toki wa, awateru.
Whenever I forget (present=about to forget) my wallet, I panic.
国へ帰る時、お土産を買います。
Kuni e kaeru toki, omiyage o kaimasu.
When I return to my country, I buy souvenirs. (Before departure, still in Japan)
国へ帰った時、家族に会います。
Kuni e kaetta toki, kazoku ni aimasu.
When I have returned to my country, I meet my family. (After arrival, already home)
暇な時、何をしますか。
Hima na toki, nani o shimasu ka.
What do you do when you are free? (Na-adjective + na + toki)
子供の時、犬を飼っていました。
Kodomo no toki, inu o katte imashita.
When I was a child, we had a dog. (Noun + no + toki)

Teacher's Advice

The Classic Trap

The most common mistake: 'When I went to Japan (行った時), I bought this.' vs. 'When going to Japan (行く時), I bought this.' The first means you bought it AFTER arriving. The second means you bought it BEFORE departing (e.g., at the airport). Always ask: When Action B happens, is Action A already finished or not yet?

A Test You Can Apply in 2 Seconds

Replace 時 with 'before/while' vs 'after' in your head. If the meaning is 'before/while doing A' → present form (帰る時 = before/while returning). If it is 'after having done A' → past form (帰った時 = after returning). This mental swap resolves 90% of toki questions without deep grammatical analysis. My students' accuracy jumps immediately once they adopt it.

JLPT Exam Patterns

  • •Choosing the correct tense (present/past) before toki based on the scenario (N4)
  • •Na-adjectives need 'na' before toki: 暇『な』時 (N4)
  • •Nouns need 'no' before toki: 子供『の』時 (N4)
  • •Reading comprehension: tracking whether the toki clause happened before or after the main clause (N4)
  • •Distinguishing 〜時 from 〜たら/〜と conditionals in sentence-completion questions (N4)

〜時 vs 〜たら: Two Different Questions

〜時 (toki) and 〜たら (tara) both translate to 'when,' which is exactly why learners mix them up. But they answer different questions. 〜時 answers 'at what point in time did this happen': it is a timestamp. 〜たら answers 'given that this happens, what follows': it is a condition, closer in spirit to 'if.'

日本に行った時、着物を買いました (When I went to Japan, I bought a kimono) is simply reporting when the purchase happened. 日本に行ったら、着物を買います (If/when I go to Japan, I will buy a kimono) frames the trip as the trigger for the purchase; it has not happened yet, and the purchase depends on the trip happening. If you can replace 'when' with 'if' in the English without changing the meaning much, たら is usually the safer choice.

Related Grammar

Conditionals: 〜たら (~tara)
Grammar guide →
Saying 'Because': から and ので
Grammar guide →
The Plain Form (Dictionary Form)
Grammar guide →
See the full JLPT N5 grammar roadmap →

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