Mavericks: Hunters Years.

Timeline

The reason I pick 10 years due to the fact that Sigma is 10 years old according to Death Battle and that he's the 1st Maverick Hunters.

Here are things that happen at this point before the event of The Day of Sigma which happen in July 4 which I headcanon 10 years in the future

April 9- 16 2114
Dr. Cain discovered X within a capsule, examine notes and specifications for X which he's a leap, and abandoned his job to bring everything from Dr. Light lab to his own.

November 22 2114
Dr. Cain used X as a blue print to create his first Reploid, Doppler who became his friend and colleague.

May 3 2115
Dr. Cain assemble a line of Reploids, the general populace happily accept this.

Memorial Day (May) 2115
The first known Maverick was Pierrot, a clown-based Reploid design for an amusement park.

Father's Day (June) 2115
The second known Maverick was Raigyan Beta, a liger-based Reploid design to be a guard of a natural zoo in Africa.

July 16 2115
The third known Maverick was Kinko Soda, a normal Reploid who was a miner. His desire to be rich and having an army of Mechaniloids caused the ideal of halting Reploids.

November 20 2115
The Mavericks Hunters were formed and Dr. Cain created the first leader who is his greatest creation, Sigma.

Thanksgiving (November) 2115
Zero was discovered as Maverick as he killed Gamma's unit, Sigma join as he fight Zero and won but was damage and Infected. Zero become a Hunter under Sigma's wing.

November 30 2115
X join the 17th Battalion and Sigma succumb to the Maverick Virus which merge with his program, become a completely infect but still sane as if he was normal. Sigma started to bring more recruits in hope to find warriors for his cause. It is the beginning of these new Hunters in training.

December 24 2115
Dr. Cain successful created these new Reploids to serve as recruit for the Maverick Hunters but Sigma have better ideas for them.