Methodology
Sources and Methodology
Japan Almanac publishes source-backed seasonal writing. We separate contemporary calendar facts, historical interpretation, card-game structure, and Koi-Koi product status.
Source Hierarchy
Preferred sources are official Japanese government and cultural institutions, Japanese national or regional museums, Nintendo Museum for Nintendo/Hanafuda material, Japan National Tourism Organization for cultural and seasonal material, and academic or museum sources where primary material is not readily available.
Launch Source Register
| ID | Source | Use |
|---|---|---|
| nintendo-hanafuda | Try Playing Hanafuda! Nintendo Museum | Used for the 48-card, 12-month Hanafuda structure and Nintendo Museum workshop context. |
| naoj-2026-moon | Chushu no Meigetsu, September 2026 National Astronomical Observatory of Japan | Used for the 2026 date of Chushu no Meigetsu and the full-moon timing. |
| naoj-calendar-wiki | Meigetsu is not necessarily the full moon NAOJ Calendar Wiki | Used to cross-check Chushu no Meigetsu and full-moon separation across years. |
| cao-holidays-2026 | National Holidays for 2026 and 2027 Cabinet Office, Government of Japan | Used for Japan's September 2026 public holidays and holiday-law notes. |
| jnto-september | Japan in September Japan National Tourism Organization | Used for seasonal travel/weather framing and September festival context. |
| jnto-tsukimi | Tsukimi, Moon Viewing in Japan Japan National Tourism Organization | Used for contemporary Tsukimi practices, offerings, and seasonal framing. |
| kokugakuin-choyo | Choyo Kokugakuin University Digital Museum, Encyclopedia of Shinto | Used for Choyo no Sekku, chrysanthemum wine, and festival history. |
| ndl-choyo | Choyo-no-Sekku (Chrysanthemum Festival) National Diet Library Image Bank | Used for historical visual source leads related to Choyo no Sekku. |
| shungate-choyo | September 9, Choyo no Sekku SHUN GATE / Washoku Association of Japan interview | Used for food-culture context around Choyo no Sekku. |
| koikoi-cultural-reference | Cultural Reference - Hanafuda & the Twelve Months Koi-Koi repository | Internal topic map only; not treated as external factual authority. |
| koikoi-rules | Koi-Koi - Rules & Variants Koi-Koi repository | Used for the current Koi-Koi ruleset and house-rule disclosure. |
| koikoi-validation | Koi-Koi Validation Koi-Koi repository | Used for internal release-status and rules-validation context. |
| koikoi-app-store | Koi-Koi Apple App Store | Used for public App Store availability, platform, price, developer, and privacy-status checks. |
| japan-prefecture-geojson | open-data-jp-prefectures-geojson npm / piuccio | Used for the events map prefecture boundaries; the package is MIT licensed and based on National Land Information Division data. |