This is a list of events that occurred in the 2240s:
- After completing his Air Dome training, Jeffrey Sinclair is promoted to fighter pilot.
- Stephen Franklin studies under Dr. Everett Jacobs at Harvard Medical School. When Franklin begins to struggle with Xenobiogenics, Jacobs takes time out to help his student, something none of the other faculty were willing to do.
- Less than a year after making fighter pilot, Jeffery Sinclair is promoted to squadron leader.
- Catherine Sakai enters Earthforce Academy.
- Michael Garibaldi works in Earthforce Security for the ice-mining operation on Europa. After several weeks on the job, Garibaldi begins to drink heavily almost every night and eventually befriends shuttle pilot Frank Kemmer, who invites him to spend a lot of time with his family, including his daughter Lianna. Lianna takes to calling him "Uncle Mike", and is often disappointed when Garibaldi turns up drunk.
- Frank Kemmer is killed in a shuttle pad explosion designed to disgrace Garibaldi, who had been making headway against the corruption at the outpost. Wishing to avoid a scandal, Earthforce officially finds Garibaldi negligent regarding the explosion and transfers him off station.
- Leo Rosen becomes convinced that his wife Sheila is having an affair with his brother Alex, in spite of their denials. The rest of the family sides with them and Leo becomes estranged.
- Lieutenant John Sheridan is assigned to the EAS Lexington under Captain Roger Sterns.
- Stephen Franklin graduates from Harvard University. Impatient at the prospect of a long medical internship, Franklin opts to leave Earth and begins hitch-hiking on starships, trading his services as ship's doctor for free passage. While passing through Septis, Franklin befriends a Markab Doctor named Lazarenn and develops a taste for a native fruit drink called orcha.
- Londo Mollari first dreams about his own death, as an old man and a one eyed Narn throttling each other.
- Leo Rosen, still convinced of his brother Alex's infidelity with his wife Shelia, speaks to Alex for what will be the last time for almost the next two decades.
- Neroon of the Star Riders enters the service of Shai Alyt Branmer.
- Londo Mollari of the Centauri Republic is assigned as a liaison with the Earth Alliance.
- On Earth, Squadron Leader Jeffrey Sinclair is assigned to train Earthforce Academy cadets at Air Dome. He first meets Cadet Catherine Sakai and immediately takes her breath away when he executes a hairpin backwards loop followed by a spinning barrel roll which almost causes her to black out. After the flight she angrily accuses him of being a dangerous show-off, to which Sinclair responds that she wouldn't cut it as a pilot and is very close to insubordination. They both soon realise it was love at first sight and begin living together. Catherine soon becomes acquainted with Sinclair's love for Tennyson.
- Dr. Robert Bryson begins his lifelong search to extend human life beyond the 110 – 115 years current Earth medicine can achieve. In his exploration of alien worlds and cultures he picks up references to Soul Hunters, that will eventually lead him to one of their Whisper Galleries.
- February, 2243
- Wednesday, May 9, 2243
- Wednesday, June 21, 2243
While hitch-hiking aboard the commercial trading ship Archimedes off Beta Durani, Stephen Franklin assists in helping the surviving passengers and crew of a Minbari vessel that crashed on nearby Theta 49. Though he does his best, Stephen lacks even a basic understanding of Minbari biology and is unable to save any of them. Still eager to learn anything he can, Franklin talks Captain Bickford into allowing him to perform full autopsies, gathering extensive medical data and making detailed notes on their DNA and biology as well as what little he could pick up about their language and culture.
- September, 2243
- Andrei Ivanov, at the request of his daughter Susan, attends a reading of Kasherov, a radical Neo-Communist writer, and ends up telling him off after he insults her.
- After spending a year living together, Catherine Sakai and Jeffrey Sinclair's relationship ends.
- Through her strong support for the cause of Mars independence, Amanda Carter meets and falls in love with Abel Horn. He convinces her to join Free Mars, a young—and then non-violent—organization dedicated to Martian independence.
- David Martell's parents die.
- Saturday, July 12, 2244
- Earth-Minbari war begins.
- Sofie Ivanov, mother of Ganya and Susan, commits suicide after being hounded by the Psi Corps for much of her adult life.
- May, 2247
- While on patrol in the Sol System asteroid belt, Ganya Ivanov is killed by a Minbari flyer during an ambush by the Drala Fi.
- Wednesday August 10, 2247
- October 10, 2247
- May, 2248
- The Mars government declares neutrality in the Earth-Minbari War, angering EarthGov and earning the scorn of many Earthers for years to come.
- The Battle of the Line takes place, signaling the Minbari surrender and the end of the Earth-Minbari War. Twenty four hours later, Jeffrey Sinclair awakens in his Starfury, with no memory of the previous 24 hours. He returns to his station and learns the War is over.
- Susan Ivanova graduates from Officer Training School for Earthforce.
- The Earth Alliance establishes a frontier colony on Tau Ceti IV, at the border of Narn and Centauri space.
- Tuesday, July 17, 2249
- Babylon 1 is destroyed when the station's infrastructure collapses during construction.
- Monday, December 3, 2249
|Before the Third Age:||20th Century and earlier 21st Century 22nd Century 2200s 2210s 2220s 2230s 2240s|
|2250s:||2250 2251 2252 2253 2254 2255 2256 2257 2258 2259|
|2260s:||2260 2261 2262 2263 2264 2265 2266 2267 2268 2269|
|2270s onwards:||2270s 2280s 2290s 2300s and beyond|