Timeline of the Sonic the Hedgehog series

Pre-Historic Era

 * Sometime between 250 million and 170 million years ago - A primitive Sonic and Knuckles live near what is now modern Metropolis City. Miles "Tails" Prower arrives from March 6, 4017 in a time machine in hopes to get back to 2017. Tails encounters a primitive Sonic and Knuckles, making them wonder about Tails' mutation and clothes, thus altering the course of history. He soon goes back into the time machine, and arrives back in the present.
 * Around 65 million years ago - Dinosaurs walk around what is now modern Metropolis City. Tails arrives after he accidentally creates a toaster time-machine, before changing the course of history.

Classic Era

 * Year 0 - Niki the Hedgehog decides to combine all the tribes into one forming a new metropolis.
 * Year 76 - After the Gods saw people using the Chaos Emeralds for evil, they create the Master Emerald to balance the Chaos Emerald's power.

Medieval Period

 * April 17, 1500 - William Prower (ancestor of Tails) stops Armybotnik (ancestor of Dr. Eggman) from taking over the Metropolis Empire.

Wild West Period (1865-1895)

 * August 17, 1880 - SonBuck the Hedgehog defeats Robitno from stealing Milea's money.
 * August 28, 1880 - The people of Metropolis City build a statue of SonBuck in his honor.

The Great Animal War (1914-1918)

 * March 2, 1914 - Jano D. Gol is killed by accident, sparking The Great Animal War.
 * April 18, 1917 - The Westside Island Empire joins the war.
 * March 2, 1918 - The animal and human races sign a note, preventing any-further war from happening.

Current Period (1945-Present)

 * February 26, 1999 - Knuckles the Echidna is born.
 * March 4, 1999 - Sonic the Hedgehog is born.
 * 2000 - Mighty the Armadillo is born.
 * 2002 - Ray the Flying Squirrel is born.
 * February 29, 2005 - Amy Rose is born.
 * April 8, 2005 - Tails is born on Westside Island as the son of Rosemary Prower and Amadeus Prower.
 * April 25, 2010 - Tails is separated from his parents for 7 years after they disappear one night.
 * May 27, 2011 - Nearly the entire Echidna tribe is wiped out after they try to seize the Master Emerald from the Chao. Tikal seals herself inside the Master Emerald with Chaos to avoid anymore destruction. Leaving Knuckles as the only survivor, and the guardian of the Master Emerald. This also causes Angel Island to rise from the ocean.
 * June 13, 2013 - Amy Rose's city is attacked by Dr. Eggman, leaving Amy as the only survivor. She uses her mother's car to escape, but it suddenly breaks down in the desert an hour later. She's soon saved by a biker gang, and the car is repaired.
 * July 17, 2013 - Little Planet at Neverlake arrives just as Amy arrives.

Sonic the Hedgehog series

 * June 24, 2014 - Sonic fights Dr. Eggman for the first time, sparking a massive rivalry.
 * July 1, 2014 - The events of SegaSonic the Hedgehog take place.
 * July 17, 2014 - Sonic meets Amy Rose and saves Little Planet from Dr. Eggman.
 * July 18, 2014 - Sonic meets Tails on Westside Island after seeing him follow him, they soon become best friends. The Evil Tails Universe is created at this point. Dr. Eggman arrives from 2019 to kill Tails and succeeds, temporarily creating another alternate universe called Dead Tails. However he's stopped when many copies of Sonic and Tails arrives to stop him. This causes many universes to be created, creating an event called The Great Timeline Creation.
 * August 25, 2016 - Tails hits a Chaos Emerald, making everyone unable to age.
 * September 5, 2016 - Dr. Eggman releases Chaos and Tikal from the Master Emerald.
 * September 5-8, 2016 - Sonic, Tails, Knuckles and Amy stop Chaos from destroying Station Square.
 * March 6, 2017 - Tails is frozen in his freezer for 2000 years by his bullies. The event is eventually erased from history after Tails arrives back from the past. This also creates a new universe called No Tails Universe.
 * September 7, 2017 - Tails is finally reunited with his parents after being separated for 7 years.
 * February 28, 2018 - Tero is presumably killed after he fights Tails in an attempt to kill him.
 * November 22, 2018 - Amy gets an abusive boyfriend named Ace, causing her to become distant.
 * January 13, 2019 - Sonic fights Amy's abusive boyfriend, ending in Ace getting arrested, and Amy being more careful.
 * January 14, 2019 - Sonic explains the story of the time Tails left him after an argument.
 * January 17, 2019 - Sonic reads the story of his ancestor of SonBuck. He also cleans his statue after it was covered in Bird Poop. Tails reads the story of his ancestor William Prower.
 * March 5, 2019 - Tails opens the Metropolis City Time Capsule after Sonic runs out of sauce on his sandwich the previous day. Sonic, Amy and Cream accidentally get stuck inside, and wait for rescue the next day.
 * April 27, 2019 - Tails and Cream go on a massive hike to their home towns after the airport closes.
 * June 22, 2019 - Many alternate versions of Sonic and Tails appear, causing a rip in the fabric of space-time.
 * June 23, 2019 - Sonic celebrates his 5 year anniversary since he first fought Eggman.
 * June 24, 2019 - Metropolis City is destroyed and Sonic is kidnapped.
 * July 1, 2019 - Freedom City is built.
 * July 10, 2019 - Sonic and Espio are rescued by Super Tails.
 * July 18, 2019 - Sonic and Tails celebrate their 5 year anniversary since they first met.
 * April 2, 2020 - Tails stops being Sonic's brother for awhile.
 * July 18, 2020 - Sonic and friends are invited to a dinner party, but Lerando the Cat and others are killed by Christine the Fox as an act of revenge.
 * July 19, 2020 - Charlie the Fox is mistakenly arrested after being framed by Christine. Sonic and Amy find out Christine's motives, and were about to be killed, until they were saved by Tails.

Future

 * March 5, 2069 - The Metropolis City Time Capsule will be opened for all of the future Metropolis City to see.

Distant Future

 * March 6, 4017 - Tails will be awakened from his freezer, and find out his Tornado 2 is now in a museum and it took 20 years to beat Eggman without him. He will use a time machine, but accidentally goes to the prehistoric era.
 * 5019 - The statue of SonBuck will still stand, and will be observed upon by future Metropolis City citizens when SonicTron does a tour of New Modern Metropolis City.