Catalyst Game Labs, the current owners of BattleTech, have divided history into six eras. The products they released are grouped in this manner. Recently newer products have included other distinct time periods by splitting the eras into sub-eras which brings the classification up to nine eras. In addition to those, four more distinct non-canon ones can be identified:
|Pre-Spaceflight||Up to 1950||Earliest referred to era, where humanity resides only on its planet of origin Terra.|
|Early Spaceflight||1950 – 2005||Early solar system restricted spaceflight.|
|Star League||Age of War (First Exodus)||2005 – 2242||The time of the Western Alliance, early Terran Alliance and earliest interstellar colonies. The Outer Reaches Rebellion results in Demarcation Declaration, the forced independence for most colonies.|
|Star League||Age of War (Second Exodus)||2242 – 2398||Colonists on marginal worlds resettle or perish. The Terran Alliance collapses; the beginnings of the Terran Hegemony and the Great Houses of the Inner Sphere.|
|Star League||Age of War||2398 – 2570||The time of the Terran Hegemony, and "civilized" warfare between the Inner Sphere houses. The first BattleMech is created.|
|Star League||Star League||2571 - 2780||The time when the Star League reached the height of its power and was destroyed by the Amaris Coup.|
|Succession Wars||Early SW||2781 – 2900||When the Great Houses vied for supremacy and many of the advances of the Star League disappeared as LosTech.|
|Succession Wars||Late SW||2901 – 3049||When the Great Houses vied for supremacy and many of the advances of the Star League disappeared as LosTech.|
|Clan Invasion||3050 – 3061||The time between the beginning of the Clan Invasion and the Inner Sphere's victory at the Great Refusal.|
|Civil War||3062 – 3067||The years in the shadow of the Federated Commonwealth Civil War.|
|Jihad||3068 – 3080||The time when the Word of Blake unleashed its Jihad.|
|Dark Age||Republic||3081 – 3130||The time since the defeat of the Blakists and the creation of The Republic of the Sphere.|
|Dark Age||Dark Age||3131 –||The time since the collapse of the HPG network causes political chaos in The Republic of the Sphere that leads to the militarization of Industrial Mechs and other civilian equipment.|
- Master Unit List: Battle Value, p. 2: "Era Legend"
- Catalyst Game Labs: "Classic BattleTech Eras"
- The Periphery, p. 12: "First Exodus"
- The Periphery, p. 14-19: "Beyond the Farthest Star" & "Inner Sphere Politics"
- Strategic Operations, p. 167: "Faction Quality Table"
- Catalyst Game Labs' forum: "Topic: The Republic era?"