Unaided, I'd have had no idea when that day was, or what I purchased (by contrast, I could regale you for hours with stories of my early scores on eBay). But according to Amazon's records, it was November 27, 1999, and I bought Jayne E. Marek's Women Editing Modernism: "Little" Magazines and Literary History. My second purchase, in January of 2000, was Sacvan Bercovitch's The Office of the Scarlet Letter.
In case you can't tell? It was my first year of graduate school.
Apart from those two initial purchases, I bought virtually no books for myself from Amazon in the years 1999-2006. I spent those years first in a college town and then in a big city--both of which had an ample supply of new bookstores--and my used and out-of-print needs were well-served by ABE. Instead, I appear to have used Amazon for two purposes: 1) birthday gifts for family and friends, 2) additions to my music and video library.
From 2000-2002 I bought myself the following:
The Exciting Sounds of Martin Denny: Exotica 1 and Exotica 2
A Tribe Called Quest, The Low End Theory
A bossa nova compilation, Nova Bossa
Louis Armstrong, Complete Hot Fives and Hot Sevens
Paris Combo, Living Room
Chris Isaak, Forever Blue
An "electro-jazz" compilation, Saint-Germain Café
Sex and the City, Season One
Who's Afraid of Virginia Woolf?
Make of all that what you will, but I'm sure you wouldn't be wrong.