Timeline

090419, 111419, 091820
This is a work in progress.

1000 AD: Modoc meets Bill Cipher and later leaves inscriptions warning future people against him. First depiction of the Cipher Wheel (aka “the Zodiac”) in the cave behind Gravity Falls Falls.

 

1941: Filbrick Pines marries Moyra Wolford
Filbrick enlists in the Marine Core, deployed to the South Pacific theater
41-45: Moyra lives with her parents and begins to develop a successful psychic counseling side-job, while she works at the perfume counter at Woolworths.
1946: Filbrick is honorably discharged (with a purple heart amongst other honors)
The Pines return to New Jersey and take over the family hardware store. Later Fil turns it into a pawn shop (seeing more money in pawn than hardware)
1947: Moyra leaves her day job to be a full-time housewife and in-home psychic consultant.
1949: Sherman Stanley Pines born to Filbrick Pines and Moyra Anne Wolford

1952: Stanford and Stanley Pines, twins, are born on June 14 and 15th. / Flora and Sally are born October 14/15 respectively.

1967: Moyra Wolford Pines born (the baby)
Sherman enlists in the Army
1968: Sherman marries Dolores Mitchell

1965: Stanley/Sally begins to work part-time with a local mechanic. Falls in love with a car that will eventually become the Stanleymobile.
1968: Stanley/Sally (16) buys the Stanleymobile

1969: Stanford/Flora (17) graduates from High School and Stanley/Sally (17) is kicked out of the house. Goes to YMCA for a short time.
Stanford/Flora begins attending Blacksmore in September; meets Fiddleford H. McGucket

1972: Stanford
1973: Stanford

1974: Richard Sanchez arrives at Blacksmore

1975: Alexander Matthew Pines, Sherman’s (26) son, born
Stanford / Florimel (23) enters Physics graduate program, receives grant and travels to Gravity Falls

1978: Sherman Pines killed in action (29)

1981 (canon inconsistency, 81 in J3, 80 in wiki):

Stanford/Florimel meets Bill Cipher (29)

1982: (30)
February: Flora reveals the plans of the portal to Tenny (The ‘Project’)
1982: July 29, Fiddleford comes to Gravity Falls

Winter: Stanley / Sally comes to Gravity Falls; Stanford / Flora vanishes through the Universal Portal

1995: Alex turns 20, engaged to Maureen Taylor(19)

2001: Mason and Mabel / Madge and Martin Pines born, August 31, to Alex and Maureen

2012: The Summer of Weirdmageddon
Mabel and Mason / Madge and Martin turn 12
Stanford/Flora returns from the Portal