WARNING! SPOILERS AHEAD!
The following timeline is a combination of information taken from the 'Friday the 13th' Wikipedia page, dialogue and various dates from the films, themselves, along with some personal fan theory. This is not a definitive or official timeline for the 'Friday the 13th' series!
PRE-FRIDAY THE 13th HISTORY
FRIDAY THE 13th ('80)

"1957" - The supposed drowning of Jason Voorhees
"1958" - Opening Sequence - Deaths: Barry, Claudette
"Friday, June 13th: The Present" - Day of Events (Presumably 1980, based on release date.) - Deaths: Annie Phillips, Ned Rubenstein, Jack Marand, Marcie Stanler, Brenda Jones, Steve Christie, Bill Brown, Pamela Voorhees
"1958" - Opening Sequence - Deaths: Barry, Claudette
"Friday, June 13th: The Present" - Day of Events (Presumably 1980, based on release date.) - Deaths: Annie Phillips, Ned Rubenstein, Jack Marand, Marcie Stanler, Brenda Jones, Steve Christie, Bill Brown, Pamela Voorhees
POST-FRIDAY THE 13th/PRE-FRIDAY THE 13th PART 2
FRIDAY THE 13th PART 2

POST-FRIDAY THE 13th PART 2/PRE-FRIDAY THE 13th PART 3
FRIDAY THE 13th PART 3

POST-FRIDAY THE 13th PART 3/PRE-FINAL CHAPTER
FRIDAY THE 13th: THE FINAL CHAPTER

POST-FINAL CHAPTER/PRE-NEW BEGINNING
FRIDAY THE 13th PART V: A NEW BEGINNING

POST-NEW BEGINNING/PRE-JASON LIVES
JASON LIVES: FRIDAY THE 13th PART VI

POST-JASON LIVES/PRE-NEW BLOOD
FRIDAY THE 13th PART VII: THE NEW BLOOD

POST-NEW BLOOD/PRE-JASON TAKES MANHATTAN
FRIDAY THE 13th PART VIII: JASON TAKES MANHATTAN

POST-JASON TAKES MANHATTAN/PRE-JASON GOES TO HELL
JASON GOES TO HELL: THE FINAL FRIDAY

POST-JASON GOES TO HELL/PRE-FREDDY vs JASON
FREDDY vs JASON

POST-FREDDY vs JASON/PRE-JASON X
JASON X

POST-JASON X
FRIDAY THE 13th ('09)
