The Internet, a global system of interconnected computer networks that has transformed the lives of billions of people across the world, turned 30 on Tuesday.

Although the origins of the Internet reach back to research of the 1960s – commissioned by the United States government to build robust, fault-tolerant, and distributed computer networks – 1 January 1983 was the day that the Internet as we know it replaced previous networking systems.

It was the day the US Department of Defence's ARPANET network fully switched from the older Network Control Program (NCP) protocol to the Transmission Control Protocol and Internet Protocol (TCP/IP) communications system, which now underpins the entire Internet.

The reason for the switch was that ARPANET had roughly 1,000 computers connected on the network at the time, and it was growing fast, so to handle the larger and increasingly complicated network ARPANET needed a new protocol.

Vint Cerf, VP and Chief Internet Evangelist at Google, was part of the team that developed a new computer communication protocol designed specifically to support connection among different packet-switched networks.

In a blog post to mark Internet's thirtieth year, Cerf, who is widely regarded as the “godfather of the Internet” said that the main emotion he remembers looking back on that day was relief.

“There were no grand celebrations – I can’t even find a photograph. The only visible mementos were the 'I survived the TCP/IP switchover' pins proudly worn by those who went through the ordeal,” he said.

“Yet, with hindsight, it’s obvious it was a momentous occasion. On that day, the operational Internet was born.”

English computer scientist Tim Berners-Lee later used the new Internet protocol to host the system of interlinked hypertext documents he invented in 1989, known as the World Wide Web.