The Warhammer 40k timeline runs from humanity’s first steps into space to the galaxy-spanning wars of the 41st and 42nd millennia. It’s the spine that holds the setting together, and once you know the big eras, almost every faction’s story clicks into place.
How the timeline is organised
Games Workshop counts time in ‘M’ numbers, where M1 is the first millennium AD and M41 is the 41st. So M30 means roughly ten thousand years before the ‘present’ of the 41st millennium, not the year 30.
The dates are deliberately loose. Most are given as eras rather than exact years, and different sources sometimes place the same event slightly differently. That’s a feature, not a bug: it lets the setting stay mythic.
The ancient eras: Terra to Old Night
Humanity spreads across the galaxy during the Dark Age of Technology, roughly M15 to M25. This is the golden age of human science, when mankind’s machines and knowledge peaked.
It ends badly. The Age of Strife (M25 to M30) shatters human civilisation into isolated worlds, warp travel becomes dangerous, and Terra collapses into warlordism. This is the ‘Old Night’ that the Imperium later defines itself against.
M30 to M31: the Emperor, the Crusade, the Heresy
At the end of the Age of Strife, the Emperor unifies Terra in the Unification Wars and launches the Great Crusade to reclaim the galaxy. At the same time, the Eldar fall and Slaanesh is born, tearing the Eye of Terror into realspace.
Then it all goes wrong. The Horus Heresy splits the Imperium in civil war, the Emperor is entombed on the Golden Throne, and the Imperium becomes the paranoid, stagnant empire fans know today.
M32 to M41: the long decline
The next ten thousand years are a slow grind. The Forging, the Nova Terra Interregnum, the Age of Apostasy, the Age of Redemption and the Waning are the big named eras, each one a crisis that reshapes the Imperium.
By M41 the Imperium is stretched thin. The 13th Black Crusade, the return of the Necrons and the Tyranid hive fleets all pile pressure onto a system that’s already creaking.
- M32: the Forging begins, rebuilding after the Heresy.
- M35 to M36: the Nova Terra Interregnum splits the Imperium.
- M36 to M37: the Age of Apostasy, a religious civil war.
- M37 to M38: the Age of Redemption, a period of aggressive purging.
- M39 to M41: the Waning, a long era of decline.
M41 to M42: the Great Rift and after
The Great Rift tears across the galaxy at the end of M41, splitting the Imperium in half and ushering in the Age of the Dark Imperium. It’s the single biggest shake-up to the setting since the Heresy.
The Indomitus Crusade follows in M42, as Roboute Guilliman returns and tries to hold what’s left together. This is where the current lore sits, and it’s still being written.
Key facts
- The timeline runs from M1 to M42, with M41 as the classic ‘present’.
- The Dark Age of Technology (M15-M25) was humanity’s peak.
- The Age of Strife (M25-M30) ended with the Emperor’s rise.
- The Horus Heresy (M31) created the modern Imperium.
- The Great Rift (late M41) split the galaxy and started the Dark Imperium era.
- The Indomitus Crusade (M42) is the current major campaign.
FAQ
What year is it in Warhammer 40k?
The ‘present’ is the 41st millennium, usually given as late M41 or early M42. Exact dates are rare, because the setting prefers eras over precise years.
How long is the Warhammer 40k timeline?
It spans roughly forty thousand years, from M1 to M42. Most of the detail, though, sits in the last ten thousand years after the Horus Heresy.
Why is there no single official timeline?
Because the lore is written as in-universe records, which are incomplete and sometimes contradictory. The Imperium itself doesn’t keep perfectly reliable history.