This timeline covers the history of the Transformers Animated cartoon continuity. Note that since the timeframes for some events are given in only vague terms, the exact ordering of portions of the timeline is a "best guess". Also, the Transformers Animated units of time "solar cycle" and "stellar cycle" both appear to be rough equivalents of an Earth year.
10 billion years ago
"4 million stellar cycles" ago
- Megatron begins his search for the missing AllSpark.
- Starscream begins attempting to destroy Megatron and become leader of the Decepticons.
- Lockdown captures Ratchet and Arcee to bring to Megatron so he can acquire the access codes in Arcee's data banks. Lockdown also steals Ratchet's E.M.P. Generator. Ratchet reluctantly uses it to erase her memory core, but not before Lockdown overloads it. Her current status is unknown.
- During open processor surgery, Ratchet receives activation codes from Arcee. He later uses activation codes to activate Omega Supreme and becomes his mentor and friend.
- Prowl lives a solitary life, dodges the draft, and is sent to Sensei Yoketron.
"2 million stellar cycles" ago
- Omega Supreme sacrifices his spark to win the Great Wars and is put into modified stasis thereafter.
- Seemingly quite some time after the AllSpark is lost, the Great War ends with the Decepticons defeated. 
"A thousand stellar cycles" ago
- Optimus, Sentinel, and Elita-1 explore an alien planet in search of a crashed Decepticon ship and its store of energon. After a battle with indigenous giant spiders, the guys escape, but Elita is left behind. She then becomes Blackarachnia. The Decepticons later find her, and she joins their ranks.
- Optimus and Sentinel join the Elite Guard, though Optimus is kicked out. Sentinel is promoted with the rank suffix of Minor.
- Shockwave infiltrates Autobot Boot Camp in the guise of Longarm, in hopes of becoming an Autobot intel bot. 
- Bumblebee goes to Boot Camp in hopes of becoming an Elite Guard soldier. 
- Ironhide goes to Boot Camp in hopes of becoming an Autobot soldier.
- Wasp goes to Boot Camp in hopes of becoming an Autobot commander. 
- Bulkhead leaves the energon farm and goes to Boot Camp in hopes of becoming an expert in Space Bridge technology. 
- Sentinel becomes the drill sergeant of Boot Camp. He gives the crew their names and, no thanks to Bumblebee, punishes them with lots of Transform-ups. JERKS! 
- Shockwave, in order to keep the suspicious Bumblebee off his trail, puts his gear in Wasp's locker. Wasp takes the fall for being a spy and goes to jail. citation needed] [
- Despite exposing the assumed spy, Bumblebee and Bulkhead are sent to become Space Bridge technicians with Ratchet, Prowl (unknown how he got here, as of now), and Optimus, while Longarm graduates from Autobot Academy, becoming head of Cybertron Intelligence, and is promoted to Prime. Bulkhead gets a higher score on his Space Bridge aptitude test than any other scientist and becomes Cybertron's top Space Bridge expert. 
1958 or 2008
- A crew of Autobot repairbots led by Optimus Prime, working on a damaged space bridge gateway, stumble upon the lost AllSpark. After a battle with Megatron and the Nemesis, their ship crashes on Earth, settling underwater in Lake Erie.
50 years later 2008 or 2058
- The Autobot repair crew awaken sometime in the 21nd century and become celebrities in the city of Detroit. 
- Sari Sumdac, daughter of Isaac Sumdac, meets the Autobots and encounters the AllSpark, which turns her her security key into an ultra-powerful MacGuffin.
- Sari shows the Autobots a new home.
- The Nemesis crash-lands on the Moon.
- Starscream and Blackarachnia arrive on Earth.
- Starscream scans a Harrier jet.
- Starscream attacks Detroit, wanting the Allspark. He fights all the Autobots, and Optimus is destroyed in the fight, but is revived by Sari's key.
- Megatron awakens and learns of his imprisonment and Starscream's betrayal.
- Prowl develops a fascination with organic life.
- Porter C. Powell cuts Prometheus Black's funding and, as a result, Black turns into Meltdown.
- Megatron helps Sumdac rebuild animatronic dinosaurs.
- Sari's key accidentally turns the dinosaurs into Dinobots. After a rampage, Prowl & Bulkhead save them and take them to Dinobot Island. Afterwards, the Dinobots learn how to transform.
- Lockdown is hired by Blitzwing to capture Optimus Prime for destroying Megatron, both unaware of Megatron's weakened state.
- Ratchet encounters Lockdown again and takes back his E.M.P. Generator.
- Nanosec is hired by Megatron to steal some Destronium for him. However, Bumblebee uses his new turbo boosters to detonate it in the atmosphere. Nanosec suffers rapid premature aging and is arrested.
- Optimus learns of Blackarachnia's true identity.
- For Sari's birthday, Megatron "helps" Sumdac create Sari's present: a musical robot named Soundwave. Soundwave eventually gains a mind of his own and begins a brief robot revolt against the humans, which is thwarted by the Autobots.
- Blitzwing and Lugnut arrive on Earth. Megatron contacts Lugnut and has the two of them go after the Allspark. The Autobots almost leave Earth, but instead, they reactivate some of their ship's defenses and defeat Blitzwing and Lugnut. Starscream returns.
- Meltdown uses the Dinobots to kidnap Sari, intending to use her as his new experiment test subject. Prowl, Bulkhead, and Police Captain Fanzone stop his plans and save Sari.
- A newly hired Sumdac employee, Henry Masterson, is fired for building technology for warfare use and then takes on the persona of the Headmaster. He steals Bulkhead's body and threatens to blow up the city, but is stopped by the Autobots.
- A monster made of space barnacles shows up outside Detroit, and Bumblebee, Prowl, and Sari defeat it.
- The Decepticons steal Sari's key. Megatron gets a new body and seemingly kills Starscream. The Autobots and Decepticons duke it out on Dinobot Island. Optimus disperses the Allspark. Sumdac is captured by Megatron.
- The Cybertron Elite Guard arrive on Earth. The Decepticons set up a base in a mine. Megatron begins his next plan to create a Space Bridge of his own.
- Porter C. Powell becomes the new CEO of Sumdac Systems. Sari is kicked out of Sumdac Tower and is revealed to have no legal identity. She goes to live with the Autobots.
- Henry Masterson is rehired by Powell. He steals Sentinel's body, but avoids going to jail.
- Random Decepticon attacks occur near Cybertron.
- The Elite Guard tries to force Optimus's team off of Earth. Starscream is kept alive by an Allspark fragment. He fails several times to eliminate Megatron, and so then sets a trap for the Decepticons, which draws the attention of the Elite Guard. He is arrested by the Elite Guard, and Optimus's team remains on Earth.
- The (hilarious) robot known as Wreck-Gar is created. He causes several mishaps, but (sort of) learns the error of his ways, saving Detroit from the threat of over-consumptive nanobots.
- Bumblebee enters an underground street race hosted by Master Disaster, which features a mysterious blue race car.
- Two oil-guzzling robots called Scrapper and Mixmaster are created and cause a bit of trouble.
- Starscream escapes captivity. Prowl teams up with Lockdown to hunt him down. Starscream creates clones of himself.
- Several of Detroit's minor super-criminals join together for a crime spree. A mysterious benefactor helps them, so long as they help him out. The benefactor is revealed to be the arms dealer Swindle. His plans are thwarted.
- Wasp escapes his captivity, swearing revenge on Bumblebee.
- Bulkhead and Bumblebee, having received a mysterious message, search for the Decepticons, while remembering their Autobot Boot Camp days.
- Blackarachnia has the Dinobots abduct Meltdown and forces him to try to remove her organic half. Optimus and Grimlock team up to help as well, but both she and Meltdown double cross everyone.
- The Constructicons show up at the Autobots' warehouse base looking for oil, and Sari is the only one there to stop them. Blitzwing takes them to Megatron, where they are made into full-fledged Decepticons.
- Megatron completes his Space Bridge with the help of the Constructicons and Bulkhead. The blue race car is revealed to be the Elite Guard member Blurr, who leads the Autobots to the Decepticons' base.
- Starscream creates several more clones of himself and launches his own attack on everyone in the Decepticon base.
- Ratchet and Sari, using the AllSpark fragments, revive the their ship's true identity: Omega Supreme. They attack the Decepticons all at once. Several characters are flung into the Space Bridge, including Megatron, Starscream (just his head) and Omega Supreme himself.
- Sari is revealed to be more than an ordinary human girl.
- Megatron and Starscream('s head) are left floating in space, bickering with each other.
- Team Chaar attacks Rodimus Prime's crew. The Autobots try to contact Cybertron. Megatron and Starscream take control of Omega Supreme. Sari upgrades her techno-organic self into a new teenage form. The Autobots cause the Starscream-controlled Omega Supreme to warp around space randomly, foiling their plot to conquer Cybertron.
- Dirt Boss is created from an old Headmaster unit. He takes control of the Constructicons, but is defeated by the Autobots.
- Wasp comes to earth for revenge on Bumblebee and switches places with him. Sentinel Prime and Jazz arrive on earth with Jetfire and Jetstorm to apprehend Wasp, who they think is an Autobot traitor. Bumblebee proves his identity and Wasp escapes. The Elite Guard realizes that Wasp is innocent and that Longarm is the real spy. Back on Cybertron, Ironhide discovers Ultra Magnus badly damaged, who reveals his attacker to have been Shockwave.
- ↑ Ratchet stated that "We've been around for 10 billion years." It is not made explicit, but from the context, it seems as if he was referring to the Transformer race as a whole.
- ↑ There are three references to the war ending "centuries ago" in "Transform and Roll Out, Part 1": two spoken by Ratchet and one by Optimus Prime. It is unclear whether this is an "Earth century" or a Cybertronian one... but Optimus' crew hadn't yet had contact with Earth when these statements were made.
- ↑ The packaging blurb on the "Transform and Roll Out!" DVD refers to the 22nd century. Additionally, Professor Sumdac mentions that his updates to Dino Drive's animatronic dinosaurs "bring[s] Dino Drive into the 22nd century."