The chronology of Lost is divided into five major parts: Pre-crash, Post-crash, Post-moving, Post-return, and flash-sideways timeline. The 2004 post-crash timeline is divided into monthly segments.
On September 22, 2004, Oceanic Airlines Flight 815 departed from Kingsford Smith International Airport in Sydney, Australia, bound for Los Angeles, California. The scheduled flight time was 13 hours. Six hours into the flight, the plane lost radio and radar contact. Two hours later the airplane experienced a catastrophic mid-air break-up into several pieces, crashing onto an island in the Pacific Ocean. Total flight time: eight hours.
- Pre-crash timeline, chronology of events prior to the crash of Flight 815. These events are depicted in flashbacks, or referenced later.
- Post-crash timeline, chronology of events after the crash of Flight 815, depicted during the first four seasons.
- Diverging timelines: After the Season 4 finale, the Oceanic Six and those left on the Island are separated by both time and space. The three years apart were covered in various ways.
- On-island: Timeshifts, 1974–1977, chronology of island events as experienced by time-jumping islanders, up to the sudden arrival of the Oceanic 6 in 1977. Depicted during the first part of Season 5.
- Off-island: 2005–2007, chronology of events taking place off the island after the rescue of the Oceanic Six. Depicted variously in flashforwards, real-time events, and flashbacks.
In 2007, Ajira Airways Flight 316 departed from LAX in Los Angeles, California bound for Guam, a U. S. territory in the western Pacific. Ten hours into the flight, the airplane began to experience heavy turbulence and a flash of bright light engulfed the plane sending some of them back in time, to 1977, while the plane and the rest of the passengers stayed in the present. The pilot Lapidus then guided the plane to an emergency crash landing onto Hydra Island runway in the Pacific Ocean.
- Post-return timeline, chronology of events on the Island after Ajira Airways Flight 316 lands. This follows events both in 1977 and 2007, as depicted in the later half of Season 5. Shortly after arriving, those who had travelled back to 1977 were able to cause the Incident which transported them back to 2007.
- Flash-sideways timeline, chronology of events in the afterlife.
- ARG events, chronology of events that have been referenced in the semi-canonical ARGs of Lost, most notably The Lost Experience.