Yes, according to Wikipedia, Sinclair Research’s second most successful computer (if we don’t count revisions of the ZX Spectrum as separate “computers”) was released on March 5, 1981. Exactly 30 years ago today.
For more about the ZX81 and the history behind it, I direct you to this excellent post, Sinclair ZX81: 30 years old tomorrow (written, as you can guess, yesterday). Spot the ad for the 16KB “massive add-on memory” expansion. 🙂 And now for some more personal history after the break…