They were first sold in shops in Japan on November 23, 1996*.
They were first sold in shops in America, Canada, Europe and Asia in May 1997.
Notice on the back, your Tamagotchi says Bandai-WiZ. Ever wonder who WiZ is? The head of WiZ used to work at Bandai. I think Bandai came up with the idea, but asked WiZ for help in actually making it (designing the characters and programming the microchip). Here's some info from WiZ Inc.'s web site: https://www.wizinc.co.jp/eng/07_01.html
*Note: Bandai seems to like to mark this anniversary with new Japanese Tamagotchi model releases. The KeiTama (sort of like a V3 but its TamaTown is accessible only through a real cell phone) was released on November 23, 2004. The EnTama (sort of like a V4) was released on November 23, 2005. The TamaSuku (Tamagotchi School - no equivalent non-Japanese model yet) was released on November 23, 2006.