On 1 January 1983, Internet forerunner ARPANET (a system developed by the US Department of Defense's Advanced Research Projects Agency) fully switched to TCP/IP (Transmission Control Protocol/Internet Protocol).
The transition came after a decade of development work on the new system, which replaced an earlier, clunkier setup, the Network Control Protocol (NCP).
Transition plans for the NCP-to-TCP/IP move were published in 1981, and some administrators began migrating soon after. But New Year's Day 1983 was the deadline, and quite a few techies found themselves cramming for it, according to Bob Braden, a member of the original ARPA research group that designed TCP.
"People sometimes question that any geeks would have been in machine rooms on 1 January. Believe it - some geeks got very little sleep for a few days," Braden wrote in a recent post to an Internet Engineering Task Force mailing list.
Of course, an Internet-like system was running long before 1983. Since 1969, researchers had been exchanging data over ARPANET, which connected hundreds of host machines at the time of the TCP/IP switchover. But the standardisation of TCP/IP laid the groundwork for today's massive, decentralised network.
In 1990, a victim of its own unplanned, unexpected success, the ARPANET was decommissioned, leaving only the vast network-of-networks we know as the Internet.