This timeline is based on a number of sources, the major ones being the movies, TV shows, books, comic books, etc. themselves; the chronology originally appearing in the book The World of Indiana Jones; and the detailed synopses appearing in Epilog magazine. An argument can be made as to what is part of the "official" Indiana Jones cannon. The numerous Indiana Jones adventures related in the different media sources sometimes contradict each other (in some cases concerning dates; in others concerning two instances where Indy encounters the same enigma for which two different explanations are given to explain the mystery). Personally, I consider the "levels of authority" for inclusion in the Indiana Jones cannon to be as follows:
MOVIES/TV/TV MOVIES - These are definitely the main sources of cannon information. George Lucas has done an incredible job of creating a character whose adventures span an entire century with creating few continuity flaws (Most notably the episode "Austria - March 1917" which takes place during the events in the ATTACK OF THE HAWKMEN TV movie - for purposes of the timeline the events in Austria have been changed to late April of 1917).
BOOKS - The series of books published by Bantam are the next level of cannon information. The books on the whole were well written and managed to capture the mysticism of the movies while still keeping a somewhat scientific outlook on explaining away the various mysteries. The books, however, do contradict the YOUNG INDIANA JONES CHRONICLES ("YIJC") in some instances (especially the date of Indy's graduation from the University of Chicago which was 1920 in the books, when in the TV show he was only in his first year of college in 1920 - for purposes of the timeline the date of Indy's graduation has been changed to 1921). It wasn't until the Indiana Jones and the Sky Pirates book that any reference was made at all to Indy's adventures as a soldier in the Belgian Army and a spy for the French Army during World War I.
YOUNG ADULT BOOKS - The series of young adult books published by Random House I still consider Indiana Jones cannon to a certain extent. The stories were entertaining and they did a good job of working in historical figures (in much the same format as the YIJC). The stories did tend to contradict other stories in that they put Indy in situations he finds himself in other stories (such as unraveling the mysteries of Stonehenge in both the young adult book, Young Indiana Jones and the Circle of Death, and the adult book, Indiana Jones and the Dance of the Giants). The series of "Find Your Fate" young adult books I do not consider Indiana Jones cannon due to the fact that these stories were mostly bad, were not intended to be part of a single Indiana Jones timeline interwoven between many different forms of media and there are numerous permutations to the storylines, so there is no one true storyline to document - for the purposes of this timeline I have used what seems to be the most "correct" version of the story.
COMIC BOOKS - The comic book stories produced by Dark Horse I also consider Indiana Jones cannon, although not to the same extent as the books. This is because the stories for the most part tend to be rather over the top (even more so than the usual Indiana Jones adventure!), not as well written and in some cases contradict other stories in that they put Indy in situations he finds himself in other stories (such as unraveling the mysteries of the Philosopher's Stone (in both the Indiana Jones and the Iron Phoenix comic book and the Indiana Jones and the Philosopher's Stone adult book). The comic book stories produced by Marvel, however, I do not consider Indiana Jones cannon due to the fact that these stories were for the most part very poor and were never written with the intention of being part of a single Indiana Jones timeline.
EUROPEAN BOOKS - The series of Indiana Jones books released in Europe, but not available in the U.S. are the final category of Indiana Jones cannon. These rank last simply because the books are in Dutch and I've never seen them. In some cases they also contradict other stories in that they put Indy in situations he finds himself in other stories (such as unraveling the mysteries of the Anasazi (in both the Indiana Jones and the Lost People European book and the Indiana Jones and the Interior World adult book).
The movies and a few of the YIJC episodes have been adapted in various different formats (adult books, young adult books and comic books). Some additional information contained in the adaptations was included and in the case of any inconsistencies between the different versions, the information in the movies and television show took precedent, followed by the books, and then the comic books.
Items surrounded by brackets "[ ]" are stories that majorly conflict with other stories (such as the Indiana Jones and the Philosopher's Stone adult novel and the Indiana Jones and the Iron Phoenix comic book) or stories that I do not consider to be part of the timeline (such as the "Find Your Fate" books and the Marvel comic book series. In the case of a conflict between stories, the one with the brackets is from a "lower" form of cannon and should be excluded from the timeline (it has been included merely for the sake of completeness).
The notations after the reference denote what the reference is:
M - Movie
TV - TV episode
TVM - TV movie
VR - Video release
B - Book
YAB - Young Adult Book
FYFB - "Find Your Fate" Young Adult Book
DHCB - Dark Horse Comic Book
MCB - Marvel Comic Book
EB - European Book