TRADITIONAL CALENDAR MONTHS

Or should I say moon-turns? This post is about languages/epochs during which the month names have referred (and still refer, in the Finnish case), to events of the seasons in both nature and traditional farmer/artisan culture (and usually overlapping with zodiac signs; for instance now we're in thermidor, ie mid-July to mid-August, the Leo month; the Finnish months, however, overlap with those of our own calendar. So it's currently thermidor and fumihirogetsuki, but elokuu, ie August). I will open the list beginning with the spring equinox, as it is tradition. I will also provide translation of the names. And you will see that they reflect the customs and climate of their respective cultures.
In this order, I will give the archaic Japanese, 1790s French, and Finnish month names (the archaic Japanese names I learned from the anime Fruits Basket):


Springtime:

• (Aries month) kurenoharu (late springtime) / germinal (of plant shoots) // (March) maaliskuu (ground moon, soil moon)
• (Taurus month) konohatorizuki (leaf-feeding moon [to silkworms]) / floréal (of flowers) // (April) huhtikuu (wood-clearing moon)
• (Gemini month) ayamezuki (iris moon) / prairial (of meadows) // (May) toukokuu (sowing moon) 

Summer:

• (Cancer month) isuzukuretsuki (moon of the last cool) / messidor (when the grain is harvested) // (June) kesäkuu (summer moon)
• (Leo month) fumihirogetsuki (publication moon) / thermidor (when it's the hottest) // (July) heinäkuu (hay moon)
• (Virgo month) odakaritsuki (rice harvest moon) / fructidor (when the fruits are harvested) // (August) elokuu (harvest moon, life moon)

Autumn:

• (Libra month) momijitsuki (maple leaf moon) / vendémiaire (of the grape vintage) // (September) syyskuu (autumn moon)
• (Scorpio month) shigurezuki (drizzle moon) / brumaire (of the fogs) // (October) lokakuu (muddy moon)
• (Sagittarius month) kagurazuki (sacred music moon) / frimaire (of the frosts) // (November) marraskuu (deathly moon)

Winter:

• (Capricorn month) umehatsuzuki (plum moon) / nivôse (snowy) // (December) joulukuu (Yuletide moon, Christmas moon)
• (Aquarius month) hatsuharu (first springtime, early springtime) / pluviôse (rainy) // (January) talmikuu (oak moon)
• (Pisces month) kisaragi (clothes-changing) / ventôse (windy) // (February) helmikuu (dew pearl moon)