What would you say it was?
Here's what a 101 year old woman answering questions on reddit (her grandson was doing it for her) said was the craziest for her time:
Running water. We used to use a cistern or a well to gather water. I remember the first time my father installed a faucet and oh my goodness, I felt like we had won the lottery!
Imagine that! This really drives home just how far we have come. In the lifespan of one human being we have gone from hand pumping water to accessing the world's data in seconds, from devices all around us, including in our pockets! How incredible it is when you 'zoom out,' so to speak, and look at the grander picture, and realize that this progress has come in the most minute little tail end of the human timescale.