What was the day of invention of electricity?

Answer 1

Electricity was never "invented" like, say, a toothbrush. Electricity was know to ancients, and its effects were seen by people who had no written language. This was lightning. Much later, static electricity was seen acting on things, and later still, crude voltage cells were constructed using chemicals. The true nature of electricity was considered and investigated by a number of experimenters over a long time before it was understood well enough to explain it.