Japanese Numbers & Dates: The Irregular Readings That Trip Everyone Up
You learned 4 is よん — so why is the 4th of the month よっか? Japanese dates and numbers hide a set of irregular readings that come up every single day. Here is the list to memorize once and never struggle with again.
Why Readings Go Irregular
Japanese has two sets of number readings: native Japanese (ひとつ, ふたつ…) and Sino-Japanese (いち, に, さん…). Dates and counters mix them, and the leftovers from the older native system survive in the most common words — especially the days of the month.
This is why 1日 is ついたち (a completely different word) and 20日 is はつか. You cannot derive these; you memorize them. The reward is that they are extremely high-frequency, so the effort pays back immediately.
Days of the Month (the irregular ones)
Days 1–10 plus 14, 20, and 24 are irregular. From 11 onward (except 14/20/24) they are regular: 〜にち.
Note: 24日 is にじゅうよっか (it reuses the よっか from 4日).
4, 7, 9 — the Numbers With Two Readings
4日 よっか, 4人 よにん, 4時 よじ
7日 なのか, 7時 しちじ
9日 ここのか, 9時 くじ
Why it matters for listening: 7時 (しちじ) and 1時 (いちじ) sound dangerously similar at speed.
Counting People
The counter for people is 〜人 (にん), but the first two are irregular: 一人 ひとり (one person), 二人 ふたり (two people). From three onward it is regular: 三人 さんにん, 四人 よにん, 五人 ごにん.
Teacher’s Note
Don’t learn these as a chart you stare at — learn them by using your own calendar. Say today’s date out loud every morning. After two weeks, ついたち and はつか will feel automatic, and you’ll have covered the highest-frequency irregular readings in the language.
Japanese Numbers Guide →
Counting & counters
Telling Time & Days →
Time, days, weeks
Japanese Counters →
Counter words & readings
Make the irregulars automatic
Nihongo Pass drills dates, times, and counters with spaced repetition and native audio — so よっか and はつか come without thinking.
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