Timeline

The Long Dark (97,445 BCE — 4000 BCE)
The time after the firing of Halo was known to the Covenant as the Long Dark, as it remains largely shrouded in mystery with only scattered hints to be found as to the civilizations that arose then. However, it should be noted that this term is drenched in Covenant bias, and notably misleading as it evokes a sense of inactivity, which was far from the case. While research into preserved Covenant historical records is pending, it is known that multiple civilizations arose in the galaxy at this time. Evidence of this can be seen in Forerunner reliquaries looted and purged of data before the Covenant's earliest explorations, reports from Forerunner constructs of ancient visitors to their installations, as well as various other examples both direct and indirect.

Some of these civilizations are no doubt still active, although well outside the human and Covenant spheres of influence. The Covenant leadership and some scholars and traders were aware of such contemporaneous civilizations, and even been in contact with them (either direct or indirect). However, the existence of such outsider civilizations was downplayed or downright hidden from the general public lest they undermine the narrative of cosmic exceptionalism the Covenant had built up around themselves. In Covenant dogma, pre-contacted civilizations were known as Children of the Long Dark, for they had not yet known the Revelation that the San'Shyuum experienced of the Divine Beyond; other civilizations were seen as barbarians by default before being "edified" by the Covenant. Yet cryptic reports of "Others" indicate the existence of one or more alien civilizations either close to or even beyond the Covenant's level of influence and advancement.

Covenant History (4000 BCE — 2525 CE)
Covenant history is recounted here as beginning from the earliest known activities of the member species, largely Sangheili and San'Shyuum at that point, rather than the formation of the Covenant as a political entity. Rather than ages, which would be too specific and too numerous, Covenant history is divided here into epochs encompassing multiple ages and reflecting broader trends within the meta-civilization in terms of expansion and political organization. This is a common way of structuring Covenant history on the macro level - though not the only one - and while undoubtedly subject to the biases and trends of Covenant scholars, it does seem useful in segmenting their history into more manageable "blocks".

PRIMEVAL ERA / PRE-COVENANT (4000 BCE-852 BCE)
c. 870s BCE: First contact occurs between the San'Shyuum Reformists and Sangheili colonists on Ulgethon. Ideological differences regarding the treatment of Forerunner artifacts result in the Sangheili executing the San'Shyuum envoys. The War of Beginnings subsequently begins.

ARCHAIC EPOCH (852 BCE — 200 BCE)
852 BCE: The founding of the Covenant is ratified with the Writ of Union.

784 BCE: The Lekgolo are incorporated into the Covenant.

238 BCE: First contact is made with the Unggoy on the remote world of Balaho. A hardy species struggling on a planet still recovering from an ancient ecosystem collapse induced by a preceding global civilization, most of the Unggoy are organized into small tribal communities with only a handful of societies at the cusp of a second industrial age. Their small numbers, low native technology level, peculiar native atmosphere and their consequent reliance on a methane supply outside it, initially makes them of little interest to the Covenant. As such, they are made a vassal-species, but no concerted effort is made to integrate them to the Covenant hierarchy, also partly due to the Covenant itself going through a minor interregnum at the time. By this point, the Covenant's conversion process has not yet fully solidified, and there is debate as to whether such lowly and primitive beings are even eligible for Salvation.

Over the subsequent centuries, the Unggoy begin to spread across the Covenant Empire, first as curiosities, entertainers and status symbols for wealthy magnates and nobles, then, more widespread servants and slaves. Increasing numbers of Sangheili aristocrats and warlords begin to foster Unggoy colonies as serfs as well as cannon fodder in their clan wars. Gradually, the Unggoy become embedded in the Covenant's power structure. Eventually, the usefulness of the species is re-evaluated, and the High Council takes steps toward a proper conversion process. Scores of Ministerial officials and missionaries are assigned to study the Unggoy, reassess their worthiness of the Great Journey, and convert them to the Covenant faith and way of life. By this point, many of the Unggoy have already accepted the Covenant religion, mostly with open arms due to the appeal of its message of universal salvation.

HIGH ANTIQUITY (200 BCE — 300 CE)
214 CE: The Unggoy are formally elevated into a full signatory race of the Covenant, becoming the second species to be assimilated to the hegemony since the Writ of Union. This served as precedent for the later Doctrine of Universal Conversion, which decreed that all beings with the capacity for thought, regardless of their level of advancement, should be assimilated into the Covenant.

LATE ANTIQUITY (300 — 1200)
500s: The first wave of Kig-Yar space exploration marks the settlement of some of their longest-standing colonies, such as T'vao, Chiraav, Vitz and Tesev. More colonization waves by various groups would follow over the centuries to come, coupled with periods of interregnum and regression. Even now, most Kig-Yar cultures across the Orion Arm can trace their origins to fewer than thirty initial communities, which also formed their core cultural paradigms in addition to Eayn's planetside nation-states. Generally, a notable number of those who did depart Eayn were the misfits and rogues of their respective communities, resulting in many of the Kig-Yar space colonies being highly eclectic and experimental in their cultures and forms of government. This rebellion was usually not solely ideological in nature, however; corporate endeavors and entrepreneurs were also motivated by the chance provided by the new frontiers to circumvent the laws and regulations of Eayn's governments.

Over time, some of the more proximate habitats (such as the orbital swarm around Eayn) were "tamed" as a result of increased contact with Eayn nations' widening cultural spheres, or otherwise stabilized into what could be called civil societies. Regardless, in the Kig-Yar meta-civilization, space habitation has generally been seen as embodying a rebellious, progressive mindset -- what some Kig-Yar philosophers refer to as the Disruptive Impulse -- and there has always been an untamed frontier across the thousands of habitats within the Y'Deio system, from the many moons and trojans of Chu'ot to the main asteroid belt and the other worlds of the system all the way to the cometary clouds.

There are even interstellar colonization efforts; or, rather, asteroid-habitats which simply strapped engines into themselves and left the Y'Deio system for parts unknown. No Kig-Yar society ever discovered slipspace travel natively, so all of these efforts are subluminal. Only two are known to have successfully reached other systems and formed self-sustaining colonies, though neither were particularly thriving. As well, an unknown number of rogue habitats exist within Y'Deio's Oort shell, many of them having retreated there prior to the Covenant contact usually for the express reason of avoiding other societies.

1112: The Yanme'e are incorporated into the Covenant. With their highly organized, top-down social structures, massive populations as well as highly advanced spacefaring technologies and weapons despite their lack of slipspace travel, the Yanme'e are some of the most formidable foes faced by the Covenant and it is only through great losses that the Covenant finally forces the monarchic superstates of the Napret system to capitulate. This grants the Yanme'e a unique place on the social ladder not only above the Unggoy but at times close to the Sangheili themselves; the interests of some of the more powerful Yanme'e queens weigh almost as heavily in Covenant decision-making as those of the higher Sangheili aristocracy. As well, the Yanme'e end up forming almost symbiotic partnerships with certain Sangheili clans near the Napret system and over time, the entire anti-spinward side of the Covenant's dominion in the Orion Arm, which has shaped some of the core cultural peculiarities of that region.

FEUDAL ERA (1200 — 1900)
This is generally seen as a time the Covenant reached the peak of the territory it could realistically control with the technology available at the time, resulting in considerable devolution of power to the regional level and cultural divergence, which would lay the foundations for tensions for centuries to come. It also saw a considerable waning in the power and authority of the Prophets and High Charity in the eyes of many, resulting in movements unthinkable in prior ages. This culminated in the Long Discord, a centuries-long period of irregular unrest and war particularly on the spinward side of the Holy Ecumene as countless homegrown religious, political and familial entities fought one another as well as High Charity's power, and ended with territorial reforms as well as the standardization of communications across the entire Covenant empire.

1300s: Differences between the major skeins on the Jiralhanae homeworld Doisac escalate into a global thermonuclear war.

1342: The Kig-Yar are incorporated into the Covenant. The Covenant caught the Kig-Yar at a time of relative interregnum, nearly two centuries past the waning of their last "golden age", such as it was. Because of their distributed governing structures (Eayn was divided among several nation-states, while most of their habitats and colonies were likewise independent), the Kig-Yar never truly presented a unified front against the Covenant. Some states surrendered outright, while others resisted for decades.

1507: The Jiralhanae are first encountered in the Covenant's spinward expansion front, making the beginning of centuries of hostilities with Covenant frontier worlds and Jiralhanae raiders.

1606: The reliquary-world Zhoist is discovered by a remote expedition following a lucky trail of breadcrumbs from epistles decoded in prior ages. Even then the world remains very remote and it will be long before effective logistical chains can be established there; for a long time, to study Zhoist was to enter a lifetime post as a hermit far from civilization, as was usually the case with such remote reliquaries that did not surrender their gifts immediately. The planet's residents were essentially an every-growing colony of hermit-monks until the first breakthroughs when the system became a nexus of activity, and even High Charity visited there and toured its immediate neighborhood. Over time, Zhoist would yield some of the most prominent technological developments in Covenant history, which will usher in major changes in the empire's internal composition and politics.

1802: From Forerunner devices and blueprints reverse-engineered on Zhoist, Covenant priest-scientists develop the Borer slipspace drive, a massive improvement on existing drive technology. The High Council quickly realizes the strategic implications of this technology, and all Ministerial fleets are to be equipped with such drives at once.

1879: The Long Discord, an ages-long period of civil wars and unrest across the Covenant's peripheries, comes to an end with Ministerial fleets, equipped with new weapons, communications and drive technology crushing the last holdouts of rebellious feudal lords.

1896: A major territorial reform known as the Coadunation marks the establishment of the primary domains as the main provincial units within the Covenant. Military power is consolidated to Ministerial armed forces, where previously, regional nobles had maintained considerable military might especially across the vast Covenant frontier.

CONSOLIDATION ERA (1900 — 2525)
The Consolidation Era marked a considerable albeit gradual re-centralization of power to High Charity and its Ministries, beginning a centuries-long decline of the Sangheili regional aristocracy as a force that was at its height capable of challenging High Charity itself- a decline that continues to this day, further accelerated by the recent consolidation of wealth and power to merchants particularly in the galactic spinward side of the Covenant's former empire.

2477: The Sacking of Ettretritan by the Jiralhanae warlord Charactus spurs the first major response by the Covenant against the Jiralhanae raiders across their frontier.

2491: Doisac is conquered by the Covenant, finally making the Jiralhanae a full subject species of the Covenant.

Human History (2000 — 2525)
See also Human technological development for a technology-oriented timeline.

2200s
2291: A team of physicists led by doctors Tobias Shaw and Wallace Fujikawa announce the first successful transition through slipspace and back. While little more than a glorified probe, the experiment proves one key point: that humans can safely enter slipspace and return. By this point, the theory of slipspace has existed for nearly two centuries, with solid proof of the para-dimensional realm existing since the late 2100s, but the trick of actually boring a hole into space-time and sending a human through in one piece turned out to be a challenge. Before Shaw and Fujikawa's breakthrough in 2291, many scientists had already given up on the possibility of a functioning slipspace incursion apparatus as a pipe dream. Had their group not succeeded, it is possible that the UEG and other powerful entities may have significantly cut the funding for slipspace projects and instead focused on the development of intra-Sol space habitat colonization as well as slower-than-light interstellar travel. By the time Shaw and Fujikawa break the news, the UEG's plans for the first interstellar colony ship are already underway, as is the vetting process for potential colonists.

With the discovery of faster-than-light travel, dozens of lucrative colonization and development projects across the Sol system collapsed almost overnight, especially around the outer worlds such as Saturn. The Venusian terraforming project died off. Some lesser colonies simply emptied out and died as the populations flocked to greener pastures across the stars.

2300s
2310: The colonization of what would later be known as the Inner Colonies begins with the launch of the UEG's first faster-than-light colony ship. Several more waves of colony ships would follow over the next five decades. With settlers chosen from among Earth's "best and the brightest", these early efforts are experimental and often risky endeavors, with several colonies struggling to maintain themselves or failing altogether. However, each colony site serves as a learning experience, and these learnings would give rise to plans for the next stage in interstellar colonization.

A widespread pioneering spirit emerged among the colonists of this initial wave, reaching even settlements that had thrived without much of the particular struggle that defined some of them. A particularly influential work in giving shape to this ideal was the widely-circulated A Pioneer's Struggle by the author Olga Palari, one of the colonists of Strauss' World in Tau Ceti. Although Palari spoke highly, even reverently, of "the Old Sun", her work had far-reaching implications in establishing trans-Solar colonists as their own identity group, and would be referenced by colonial authors, philosophers and ideologues for centuries to come. In most of the Inner Colonies, this philosophy faded to the background after the onset of the Domus Diaspora and the subsequent economic, cultural and political integration of Sol and the Inner Colonies; however, many Outer Colonial settlers would adopt it as one of the foundational texts of their emerging cultural identity around a century later.

2362: The launch of the Odyssey Fleet marks the start of "assembly-line colonization" with standardized terraforming equipment, prefab colony starter units and other equipment pioneered over the previous half century by humanity's first colonization efforts. Colonization becomes cheaper, safer and more accessible, though applicants are still carefully vetted by the UEG. This is widely regarded as the beginning of the Domus Diaspora, humanity's first major wave of expansion outside Sol.

Some Inner Colonies settled during the Domus Diaspora would retain populations from the first half century of colonization, only for their worlds to be subjected to massive new waves of settlement enabled by the new technology. While on some worlds, the integration of the original "Pioneers" with the new colonists proceeded without issue, there were a number of sites where the divides between the two groups became too great to overcome, with accusations of the Pioneers being treated as second-class citizens or outright exploited by the Diasporan "elite". Such excesses did occur on two worlds, albeit by select CAA staffers and the less scrupulous colonization contractors, but radical elements of the Pioneer populations did not see the distinction between these institutions and the general Diasporan population.

Tales of scattered incidents, often exaggerated in the telling as they crossed the light-years, circulated among the populations of the emerging Inner Colonies. Riots and peaceful protests escalated into conflict. This eventually gave rise to the Inner Colony Wars in the late 24th and early 25th centuries. Although the political reality was often more complex and muddled, the general dividing lines in the Wars were between the "Pioneer" and "Diasporan", or old and new, colonists on the half dozen worlds where such a divide existed.