Open-air market held on the day of the tori (rooster) during November—a tradition that has continued since the Edo period. The roosters is one of the 12 animals on the Zodiac and so occurs every 12 days, meaning that on any given year there are 2-3 market days. The Asakusa tori no ichi is held at Chokokuji Temple and the nearby Otori Shrine, both of which are about 1km north of Sensoji. The tori no ichi in Asakusa is the most famous, but other events are held throughout the city, most notably at Hanazono Shrine in Shinjuku.
Event details are taken from official sources whenever possible. It is always prudent to check the official event website before attending to make sure that there have not been any changes. If you know of an error in the calendar, then please let me know through the contact form.