Kan or Not: Durations Versus Points in Time in Japanese

Why sanji and sanjikan are two different words

English uses the same noun for both jobs. Three o'clock and three hours share the word three, and the difference lives in o'clock and hours. Japanese does the same thing, but the marker is a suffix that learners often treat as decoration. Ji names a position on the clock face. Jikan names a measured quantity of time. Once you hear them as two separate nouns rather than one noun with an optional ending, the rest of the system falls into place quickly.

This matters because the two nouns then take different particles and answer different questions. Nanji desu ka asks for a clock reading and expects sanji desu. Nanjikan desu ka asks for a length and expects sanjikan desu. If you answer a how-long question with a clock reading, a Japanese listener will hear an appointment time and wait for the rest of the sentence that never comes.

The time word map

Read the two columns as separate vocabulary lists rather than as one list with a modification. Sangatsu and sankagetsu are not variants of each other; one is the name of a month and the other is a quantity of months. The same goes for mikka meaning the third of the month and mikka meaning three days, which are genuinely the same word doing two jobs, and only the sentence tells you which.

When kan is required, optional, or wrong

Where kan is optional it is not meaningless. Adding it pushes the phrase toward a measured, deliberate span: gonen Nihon ni imashita reports five years in Japan, while gonenkan Nihon ni imashita frames those five years as a continuous stretch you are counting. In speech people drop it constantly, especially with days and months, so treat the optional column as a stylistic dial rather than a rule to enforce.

The two required rows are where beginners lose marks. Ji without kan is always a clock reading, and shū without kan does not stand alone as a counter at all. If you want to say for two weeks, nishūkan is the only option.

The particle rule that finishes the job

The pattern behind the table is simple. Ni pins a fixed, absolute point that you could write on a calendar or a clock. Words that shift with the moment of speaking, such as kyō, ashita, konshū and rainen, do not take it, and neither do repeated periods such as mainichi. A duration is not a point at all, so there is nothing for ni to pin, and it attaches directly to the verb.

The last row is the useful exception. When you count how often something happens inside a stretch of time, the stretch does take ni: isshūkan ni sankai jimu ni ikimasu means I go to the gym three times a week. Here the week is not a duration of the going, it is the frame the count sits inside. Our general particles guide covers ni's other jobs if you want the wider picture.

Minimal pairs to say out loud

These pairs change one thing only: the time expression. Say them in sequence and let your mouth learn that the second line of each pair has nothing between the number and the verb. The most persistent learner error is not choosing the wrong counter, it is adding ni to a perfectly good duration out of habit.

Asking and answering how long

Question words follow the same split. Nanji asks for a clock reading, nanjikan asks for a number of hours, nannichi asks for a number of days, and dono kurai asks for an unspecified amount that the answer can fill in with any unit. Dono kurai is the safe choice when you do not know whether the answer will be in minutes, days or years, and it is what people actually use most often in conversation.

Notice the de in sanjuppun de and nijikan de. That de marks the amount of time a completed action fits inside, so it means in or within rather than for. Sanjikan benkyō shimashita says you studied for three hours; sanjikan de owarimashita says the whole thing was done inside three hours. Learners who reach for de on every duration end up saying the second when they mean the first.

Spans with kara and made

Kara and made draw the two ends of a stretch, and the stretch they draw is made of points, not durations. Kuji kara goji made is nine o'clock to five o'clock, two clock readings joined into a span. You cannot build the same phrase from jikan, because a duration has no start point to mark. This is a useful sanity check: if a time word sits in front of kara or made, it should be a point word.

The last three rows hide a third contrast. Made marks a continuous state that runs right up to a moment, while made ni marks a deadline the action must happen before. Goji made machimasu is waiting all the way to five; goji made ni dashite kudasai is submitting at any moment before five. Our dedicated made and made ni post takes that pair apart in detail, but the shortcut is that made ni almost always appears with a one-off action verb.

Approximate time: goro versus gurai

The vagueness words split along exactly the same line. Goro attaches to a point and means around that moment. Gurai, also said kurai, attaches to an amount and means roughly that much. Because both translate as about in English, learners mix them, and sanji gurai ends up meaning about three hours' worth of three o'clock, which is not a thought anyone has. Goro also normally swallows the ni, so sanji goro ikimasu is more natural than adding ni after it.

Days are the awkward set

Days break the neat pattern in two ways. First, the same forms cover both jobs from the second onward: mikka is the third of the month and also three days. Second, one day has two completely different words. Tsuitachi is the first of the month, and ichinichi is a duration of one day. Ichinichi also appears in ichinichi-jū, meaning all day long, which is the phrase you will actually reach for most often.

From two days upward you can add kan freely, and futsukakan, mikkakan and yokkakan are all natural when you want the span to sound deliberate. In everyday speech people often drop it, so mikka yasumimashita and mikkakan yasumimashita both mean I took three days off, with the second sounding slightly more measured.

The mistakes worth hunting down

• Sanjikan ni okimashita for at three: drop the kan and the sentence becomes sanji ni okimashita.
• Sanjikan ni nemashita for slept three hours: drop the ni, because a duration never takes one.
• Isshū benkyō shimashita: shū cannot stand alone, so use isshūkan.
• Ashita ni ikimasu: relative time words such as ashita, kyō and raishū take no particle.
• Mainichi ni renshū shimasu: repeated periods take no particle either.
• Sanji gurai kakarimasu when you mean about three hours: use sanjikan gurai.
• Nijikan de hanashimashita when you mean we talked for two hours: use nijikan hanashimashita.

A five-minute daily drill

• Say your day as six point sentences, each with ni, checking that every time word is a clock reading or a date.
• Say the same day as six duration sentences with no particle at all, and pause before the verb to prove nothing is missing.
• Answer nanjikan neru no and nanji ni neru no in the same breath, so the pair stays linked.
• Convert three of your duration sentences into kara and made spans, which forces the point words back out.
• Finish with two gurai sentences and two goro sentences, and say aloud which one is an amount and which is a moment.