For the fans of Person of Interest

ARPANET was hacked on 27th October 1980 which introduced complete halt in the network.
Sources:
1) http://www.zakon.org/robert/internet/timeline/#1980s
2) http://computer.howstuffworks.com/arpanet4.htm = Read the last section of "Hacking Arpanet"

The exact date is mentioned in Person Of Interest when Harold hacked the ARPANET and was being investigated by the department of defense.
Sources:
1) http://personofinterest.wikia.com/wiki/Harold_Finch  =  Read the section of 1980, 27 October.

What an accuracy! Glad to know that. :)