The Festival of Twilight
"It is a might strange that the whole world shares a calendar, I'll give you that. But I can tell you how I think it happened. Titania and Mab got right sick of places not bein' ready for festivals and such when they visited, to say nothing of the Erlking's wrath when people weren't prepared for the hunt. So Titania sent out emissaries with calendars to the whole world. Course Fae not really understanding time to good, it was based on the Long Cycle of the Moons back when us mortals were just learning to count past fingers and toes. So some smart kid took the Summer Queen's 10,764 day calendar and divided it up to a nice 468 day year with 12 months of 39 days each, probably because they wrote it in stone and that was the size he could carry" - Jasper Cameron, Leader of the Bronze Ravens
The Festival of Twilight is held the world over once every 39 days, when both the Fae and Darkening moons are New. On that night two separate locations on Kohtalo are connected to each other through the Twilight Realm. The festival grounds traditionally has 10 exits, although all but 2 are usually blocked. These "gates" correspond to the cardinal directions in the Fae and Cysgodol and are as follows: The Dayward Gate and Nightward Gate are unblocked and will lead to the corresponding area of our world, and traditionally people will enter the Nightward gate at dusk at the start of the festival and exit the Dayward gate the following dawn, assuming they did not loose track of time or misplace their sense of direction. The other gates are in pairs, one to Fae and one to Cysgodol, and are in the directions of Summer, Winter, Order(safety), and Chaos(danger) It is worth noting that the last 2 gates listed are rough translations of ideas, and are the 2 directions that change most often both Fae and Cysgodol. The locations on Kohtalo, the Fae Realm, and Cysgodol that are connected are determined by the phase of the Ethereal Moon, with the largest festivals happening when the Faerie courts are connected, occurring on the Solstice every 11.5 years.
In modern times, with anchor platforms constructed, the Twilight Market is less dangerous than in times past, when its borders were less defined. It is believe that the tendency of the markets borders to wander is what lead to the widespread tradition of encircling a fairground in a length iron chain.