暦・令和・平成: Dates, Days, and Eras

Japan keeps time on two calendars at once. There is the familiar Western calendar (西暦, せいれき) — 2026 and so on — and there is the imperial era calendar (和暦, われき), where the same year is 令和8年, "the 8th year of the Reiwa era." Both are live and everyday: your phone shows 西暦, but a bank form, a driver's licence, a coin, or a government document will often demand the 和暦. This page shows you how to read and build a complete Japanese date — year, month, day, and weekday — and how the era names 令和・平成・昭和 (元号, げんごう) fit into it. The individual counters are drilled on their own pages; here we assemble them into real dates and tie in the era system a resident actually has to navigate.

The order: big to small

The first thing to internalize is the order, which is the reverse of the American month/day/year. Japanese always runs largest unit to smallest: year → month → day → weekday.

Written out fully, a date looks like 2026年5月3日（金） — year, month, day, and the weekday in parentheses. The weekday comes last, often abbreviated to a single kanji: （金）for Friday, （日）for Sunday. This big-to-small logic is the same one behind Japanese addresses (prefecture first, house number last) and even the way you say your name (family name first).

Naming the months: 〜月（がつ）

Months are simply number + 〜がつ — "month one, month two" — with three irregular readings you have to watch. April, July, and September do not use the counting readings you'd expect.

The three to lock in as month names: 4月＝しがつ (not よん), 7月＝しちがつ (not なな), 9月＝くがつ (not きゅう). "What month?" is 何月（なんがつ）.

The days of the month: the great irregular block

Here is the hard part of the Japanese calendar. Days 1 through 10 of the month do not use Sino numbers at all — they use readings drawn from the ancient native counting roots, and they simply have to be memorized as a set. There is no rule to derive them; this is the single most irregular counter in the language.

From the 11th on, the counter finally behaves — Sino number + にち — with three stubborn holdouts: 14日＝じゅうよっか and 24日＝にじゅうよっか (keeping the native よっか for "4"), and the wholly irregular 20日＝はつか（hatsuka）, a fossil of the old word for "twenty" (the same はた inside 二十歳 はたち). "What day of the month?" is 何日（なんにち）.

The days of the week: 〜曜日（ようび）

Each weekday is one kanji + 曜日 (よう + び, "day of the shining body"), naming one of the seven classical luminaries — the sun, the moon, and the five visible planets, each tied to one of the five elements.

"What day of the week?" is 何曜日（なんようび）. Named weekdays are specific points in time, so they take the particle に when marking when (土曜日に). The full mnemonic — and why these match French lundi, mardi and Spanish lunes, martes — is on Days of the Week (曜日).

The era system: 令和・平成・昭和

Now the piece that catches every newcomer off guard. Alongside 西暦, Japan counts years by imperial era（元号, げんごう）. Each era has a name, and its years count from 1. Change eras and the count resets. The three you must recognize as a resident:

The current era is 令和, which began in 2019. To convert, remember that 令和 year = Western year − 2018: 2024 is 令和6年 (Reiwa roku-nen), and 2026 is 令和8年 (Reiwa hachi-nen). One quirk: the very first year of any era is not 一年 but 元年（がんねん）, "the founding year" — so 2019 is 令和元年, Reiwa gannen.

Why two calendars at once matters

Step back and see the whole system: Japan didn't replace its calendar when it adopted the Western one — it kept both, side by side, and assigned them different jobs. Casual and international contexts use 西暦; officialdom, tradition, and generational identity lean on 和暦. This is why 平成 and 昭和 aren't just year-ranges but social markers — 昭和 evokes the postwar decades, 平成 the bubble-and-after generation, and calling something 昭和っぽい ("so Shōwa") means "old-fashioned, retro." A resident has to move fluidly between the two, because a single afternoon of errands can ask you for a Reiwa birth year on a form and a 西暦 expiry date on a card. Master the conversion (era year = Western − 2018 for Reiwa, − 1988 for Heisei) and the double calendar stops being a trap.

Common mistakes

The number-one date error: regularizing the 1st. いちにち exists, but it means "one day" as a length of time. The date is always ついたち.

Once learners see that the 11th–19th are regular, they assume the 20th is too. It isn't: はつか, a fossil of the old word for "twenty."

Because 4 is usually よん when counting, learners produce yon-gatsu. But the month name is しがつ (and 9月 is くがつ, not きゅうがつ).

English speakers sometimes calque "the 3rd of May" and put the day first. Japanese is strictly year → month → day → weekday.

The opening year of every era is 元年, never 一年 — fixed usage across 昭和元年, 平成元年, 令和元年.

Key takeaways

• A Japanese date runs big-to-small: 年 → 月 → 日 → 曜日 (2026年5月3日（金）).
• Month names are number + がつ; irregulars 4月 しがつ, 7月 しちがつ, 9月 くがつ.
• Days of the month have a big native-root block 1日 ついたち … 10日 とおか, plus 20日 はつか and 14日／24日 じゅうよっか／にじゅうよっか — memorize, don't derive.
• Weekdays are luminary + 曜日 (月火水木金土日), asked with 何曜日, taking に for "on [day]."
• Japan runs 西暦 and 和暦（元号） in parallel: recognize 令和 (2019–), 平成 (1989–2019), 昭和 (1926–1989); era year 1 is 元年（がんねん）; official forms often demand the era year, so it's a survival skill, not trivia.