When did ARPANET officially transition to using the TCP/IP standard, marking a significant milestone in Internet history?

The transition of ARPANET to the TCP/IP standard on January 1, 1983, marks a pivotal moment in the evolution of the Internet. This shift established TCP/IP as the foundational communication protocol suite that allowed diverse computer networks to interconnect and communicate, effectively creating a unified "network of networks" that we now recognize as the Internet.

This milestone ensured that various types of networks could work together, forming the basis for the protocols that still govern Internet traffic today. TCP/IP's adoption enabled interoperability among different computer systems and paved the way for the rapid expansion of the Internet in the following years.

The other dates mentioned in the options are significant in their own contexts, but specifically, January 1, 1983, is the date when the transition to the TCP/IP standard was officially completed, leading to the eventual growth and widespread use of the Internet as we know it today.