There are 2 alternate timelines because Wolverine travels through time and changes the past.
1962: X-Men: First Class
1981: X-Men: Origins Wolverine
2000: X-Men
2003: X2: X-Men United
2006: X-Men: The Last Stand
2013: The Wolverine
2023-->1973: X-Men: Days of Future Past
Then the past changes:
Alternate 1983: X-Men: Apocalypse
Alternate 1992: X-Men: Dark Phoenix
2016: Deadpool
2018: Deadpool 2
2019: The New Mutants
2029: Logan