"May 5th is MEIKO Day". It comes from the play of words when you can read the date as the actual word. This time it's May5 -> MeiGo -> Meiko. With English reading of month and Japanese one of day. (description by Nefere)
Event on Booth.
An annual festival hold in Shanghai, organized by the famous video sharing service.
Doujin fair dedicated to original works.
Live video viewing event.
Name originates from "Friends".
Series of Kagamine Rin/Len only events.
Music Media-Mix Market, or M3, is a bi-annual flea market for independent music makers to sell their goods.
An annual UTAU-only event.
The MMD Cup is a tournament-style animation contest in which participants are given a theme and are tasked with making an animation with the software, MikuMikuDance (MMD).
Vocaloid event where artists sell albums and other merchandise. Lately UTAU artists have participated as well.
VOCALOID only event in Taiwan, China.
Kagamine Rin & len only event
Unofficial Magical Mirai after party.
A concert event dedicated to Nico Nico famous users
Nico Nico Chokaigi is a yearly convention/festival hosted at Makuhari Messe, Chiba (near Tokyo). Generally there's multiple Vocaloid-related events as well, such as The Voc@loid M@ster.
Series of concerts held near Miku's birthday (August 31st).