This timeline is based on evidence provided by the Harry Potter Lexicon - thank you!
1981
(exact date unknown) - Luna Lovegood is born, to witch and wizard parentage.
We assume that Luna is born the same year as Ginny, however, it must be acknowledged that
she could be in the same situation as Hermione, if she was born any time after September 1st 1980.
1990
(exact date unknown) - Luna witnesses her mother's death. She dies from a fault
in one of her own magical experiments.
Book Citation: "She was a quite extraordinary witch, you know, but she did like to
experiment and one of her spells went rather badly wrong one day. I was nine."
1992
September 1st - Luna starts at Hogwarts and is consequently sorted into Ravenclaw.
Book Citation: "Luna's in my year, but in Ravenclaw." - OotP169
1994
Luna begins Care of Magical Creatures classes.
Book Citation: "I'll be quite glad if he has," said Luna, "[Hagrid] isn't a very good teacher,
is he?"
1995
September 1st - Luna meets Harry Potter, Neville Longbottom, Hermione Granger and Ron Weasley on the
Hogwarts Express.
September 3rd - Luna informs Harry Potter that she believes him.
October 5th - Luna attends a recruitment for Dumbledore's Army in the Hog's Head.
October 9th - Luna attends the first meeting of Dumbledore's Army.
November 2nd - Luna wears her lion's hat to the Gryffindor/Slytherin Quidditch Match.
December 18th - Last DA meeting for the term.
1996
February 14 - Luna meets with Hermione, Rita Skeeter and Harry in the Three Broomsticks.
She is sitting in on an interview that she then arranges with her father to be published in
The Quibbler.
March 23 - The Quibbler containing Harry's interview is published. Luna gets her father to
send Harry a copy.
March 24 - Luna announces The Quibbler is reprinting, fastest-selling-ever issue.
May 30 - Luna wears an eagle hat to the Quidditch Final.
2006
September 25 - Photographic evidence of Luna first appears