From Wired Magazine: http://www.wired.com/thisdayintech/2011/09/0919fahlman-proposes-emoticons/

September 19th, 1982: At precisely 11:44 a.m., Scott Fahlman posts the following electronic message to a computer-science department bulletin board at Carnegie Mellon University:

19-Sep-82 11:44 Scott E Fahlman : -)
From: Scott E Fahlman

I propose that the following character sequence for joke markers:

: -)

Read it sideways. Actually, it is probably more economical to mark things that are NOT jokes, given current trends. For this, use:

: -(

With that post, Fahlman became the acknowledged originator of the ASCII-based emoticon. From those two simple emoticons (a portmanteau combining the words emotion and icon) have sprung dozens of others that are the joy, or bane, of e-mail, text-message and instant-message correspondence the world over.

So happy smiley face emoticon day to all of you… even if it IS a Monday!