Well, presumably if you can figure out the Judgement Days, you can figure out the number of timelines. However, not all of the movies fit together in the same continuity and the Sarah Connor Chronicles only correlates with the first two films.
Pre-Terminator: Kyle Reese isn't John Connor's father, but is sent back in time to be his protector, and becomes his father. Original Judgement Day is unknown.
Terminator: In this timeline, Kyle Reese is already destined to be John Connor's father. Judgement Day is August 29, 1997 (per T2)
T2: Judgement Day: Cyberdyne Systems is a direct result of T-800 from Timeline #2. Judgement Day is postponed.
T3: Rise of the Machines: Skynet is created by Katherine Brewster's father and Judgement Day happens on July 25, 2004.
Things go to pot here, because Sarah Connor Chronicles ignores T3, and John and Sarah jump for a future after that Judgement Day. Additionally the resistance and Skynet are sending lots of people back all over the place trying to change the timeline.
Sarah Connor Chronicles: Cameron (the terminator) says Judgement Day is April 21, 2011.
Sarah Connor Chronicles: Jesse comes from a different timeline than Derek Reese, but does not state when her Judgement Day is.
Again, there might be many many more timelines that are created due to time meddling.
Terminator Genisys: A new timeline is created when a T-800 goes back to 1973 to protect Sarah Connor from a different assassination attempt. Judgement Day is again August 29, 1997
Terminator Genisys: With the destruction of the T-800 from the Protector, Judgement Day is postponed to 2017. Kyle learns this via new memories created by the shifting timeline. Kyle and Sarah travel forward in time from 1984 to 2017.
Terminator Genisys: Cyberdyne is destroyed, but the core systems survive, and Judgement Day is postponed, yet again.