According to Wikipedia it was the year that Queen Elizabeth officially opened the Opera House and AC/DC performed their first major gig in Sydney. It was also the year that this fella was born - 36 years ago today.
(The one on the left by the way).
Just as momentous an event as those other little factoids if you ask me ;) And would you believe I have been celebrating birthdays with this man since he turned 18? You do the math!