Matt, the birthday depends on how you define the word Internet. If you define the Internet as the global, public service of mainly email and 3w as we know it today - available to everyone with a PC and a telephone - then 1994 is the correct answer.
"Global" is unfortunately not strictly the correct word. Yesterday I got an email from a nephew, who is backpacking in Thailand, telling that tomorrow he will fly to Burma where Internet is prohibited by law - no more hotmails for his old uncle!!! The dictators want their people to stay uneducated.
But when talking email, then large companies and (groups of) universities have run closed networks for much longer time. For instance my company had its own global email network 20 years earlier based on IBM mainframe computers and IBM's PROFS software (PRofessional OFfice System). 3w were much simpler systems, and they were normally called Bulletin Board Systems, or BBS's. Other systems, mainly at universities, were based on technology similar to what was developed into the Internet of today.
So depending on definition of the word Internet you may dig bag to any date back to the mid fifties when the US Air Force first time tested a communication link between radar stations on the iceshelf of Greenland to Thule Air Base in northern Greenland.
Too bad that the Internet was invented so late. Hitler used the newly invented monopol one way communications - the radio and the movie - to create WW 2. In the age of public two way communication he wouldn't have had a chance. In the end it will be what eliminates guys like Milosevic.
One day the Internet will be the technology which unites people all over the world much the same way as the railways made it possible for Bismark to unite a few dozen small principalities into Germany - only Luxembourg was "left over".
Always keep your number of landings equal to your number of take-offs