"The annual 23 September celebration started in 1999 as International Celebrate Bisexuality Day, created by three bi activists from the USA – Wendy Curry of Maine, Michael Page of Florida (also well-known as the creator of the bisexual flag), and Gigi Raven Wilbur of Texas. It has also been variously known as Bi Pride Day, Bi Day and Celebrate Bisexuality Day. The use of the name Bi Visibility Day instead started with UK with Jen Yockney, and spread first across Europe and then further around the world. Jen says of the name: “It’s deliberately bi and not bisexuality so as to be inclusive both of people who are bisexual and biromantic but perhaps not both: for example, to be clearly inclusive of asexual people who may want romantic relationships regardless of gender.”
Back in 1999, it was marked in the USA, UK, Canada, Japan and South Africa: this list has grown to more than 30 countries in recent times." - About – Bi Visibility Day