Distant past

The distant past is a period before the 1st millenium.

Hundred billion years ago

 * In 97,445 BCE; Forthencho, acting as a messenger for the Gravemind, stated that the Domain had around hundred billion years of "life-patterns and living wisdom".

Before life

 * The great Glow occurs in the galaxy.

Over half a billion years ago

 * In 97,445 BCE, during a debate with Mendicant Bias, the Precursors were hinted by the Gravemind to have accumulating a vast reserve of rules based on experiences and disputes.

Around 15 million years BCE

 * The Precursors seeded the species that would come to be known as Forerunners on the planet Ghibalb.

Around 10.1 million years ago

 * The Forerunner Warriors were considered the highest rate.
 * Star roads were placed around Charum Hakkor.
 * The Precursors choose early humans to be the next species to carry the Mantle. Desiring to seize the Mantle for themselves, the early Forerunners rebel against the Precursors and wipe them out almost entirely.
 * After the Forerunners hunt down all of the Precursors in the Milky Way galaxy. The remains of the Precursors retreat into the Large Magellanic Cloud; the Forerunners' Warrior fleets pursue them via probability mirror-reconciled slipspace portals and proceed to finish their work.
 * A number of Forerunners who conscientiously object to the complete destruction of the Precursors in the Large Magellanic Cloud are exiled on a barren planet within the Tarantula Nebula; these Forerunners later remain as the only surviving population of the expedition.
 * In the face of extinction, most of the Precursors reduce themselves to inert powder, intending to regenerate their forms later. However, one intact specimen remained in deep stasis and is buried within a remote asteroid a million years afterward.
 * In the Large Magellanic Cloud; two Precursors escaped the genocide, where some Forerunners hide them; but they die and become flowers containing their genetic code.
 * Following the battle in the Large Magellanic Cloud, the remaining Forerunners on the ships sacrificed themselves than return with what they did; leaving the abandoned Forerunner ships in the Large Magellanic Cloud to slowly decay.

Around 9.1 million years ago

 * In the Large Magellanic Cloud; two Precursor seeds germinate.
 * The Primordial, a dormant Precursor, is said to have arrived on the edges of the galaxy.

Around 1.1 million years ago

 * The Forerunner Theoretical known as Boundless begins to study a particular star within the Path Kethona galaxy. When she continues her work in defiance of Warrior orders to the contrary, she is eventually prosecuted, her studies are suppressed, and she is forced to enter a Cryptum.
 * A thousand years later, Boundless' Cryptum is opened and it is discovered that she has died inside due to a malfunction in the Cryptum, supposedly resulting from sabotage. Her former students discreetly dispose of her body. After Boundless' death, the entire Theoretical rate is absorbed into the Builders.

Around 1 million years ago

 * In the Large Magellanic Cloud; two Precursor seeds bloom.

Around 600,000 years ago

 * A Forerunner civil war takes place, where Jat-Krula was used as a strategy, where it was bypassed by a Legion of Warrior commanders.

Around 150,000 years ago

 * The Forerunners are claimed by some records to have risen as the preeminent species in the Milky Way Galaxy by advancing technological discoveries gathered from the remnants left by prior ancient races. Believing themselves responsible for the lives of all those less advanced then they, the Forerunners initiate the Mantle.
 * According to Forerunner research, the Ancestors, were believed to have "moved their interstellar civilization outward along the galactic arm" around this time, possibly to escape Forerunner control.

122,000 years ago

 * 122,990 BCE

112,000 years ago

 * 112,329 BCE

111,000 years ago

 * 111,209 BCE

110,000 years ago

 * 110,962 BCE
 * 110,255 BCE

108,000 years ago

 * 108,992 BCE

107,000 years ago

 * 107,564 BCE
 * 107,472 BCE
 * 107,445 BCE

106,000 years ago

 * 106,538 BCE
 * 106,498 BCE
 * 106,445 BCE

101,000 years ago

 * 101,295 BCE

100,000 years ago

 * 100,040 BCE

98,000 years ago

 * 98,445 BCE
 * 98,401 BCE
 * 98,395 BCE
 * 98,119 BCE

97,000 years ago

 * 97,764 BCE
 * 97,745 BCE
 * 97,645 BCE
 * 97,495 BCE
 * 97,464 BCE
 * 97,445 BCE (Halo Array fired)
 * 97,421 BCE

57,000 years ago

 * 57,448 BCE

40,000 years ago

 * 40,000 BCE

29,000 years ago

 * 29,823 BCE

2200s BCE

 * 2200 BCE

2100s BCE

 * 2100 BCE

1040s BCE

 * 1041 BCE

1010s BCE

 * 1018 BCE

950s BCE

 * 957 BCE

930s BCE

 * 938 BCE

920s BCE

 * 921 BCE

910s BCE

 * 918 BCE

870s BCE

 * 876 BCE

860s BCE

 * 860 BCE

850s BCE

 * 852 BCE
 * 851 BCE
 * 850 BCE

790s BCE

 * 791 BCE

780s BCE

 * 789 BCE
 * 784 BCE

640s BCE

 * 648 BCE

480s BCE

 * 480 BCE