Doom 4 timeline

This is the timeline from Doom (2016) which apparently takes place in an alternate timeline to the original series (but shares the same hero from both).

Background
Reboot universe's timeline is generally considered to be a parallel universe to the original Doom, or Doom 3. Though its not exactly clear how it ties into previous series, other than Doom 64/Lost Levels ties into it, according to the developers (and Quake Champions Doom Slayer biography previously linked all of the characters together as well).

Doom 2016's dates are based on MTC (Mars Coordinated Time) (although it doesn't appear to be correctly used as MTC doesn't calculate months or years, and months and years are given in the game). One possiblity is that the dates are really supposed to be "My" (Mars Years) dating system... If the dates given in the game are My, MY2149 would be extremely far in the future, roughly in the 4000s on earth (an earth year is roughly half of that of Martian year). This would technically place Doom (2016) and Doom Eternal in the far future even beyond 2145/46 dates in Doom 3, or the 21st century dates in the classic SNES Doom timeline. Essentially placing events in the 4th millenium CE (400th Century)...

If the dates are instead intended to be based on Earth time (as the earth based months indicate) it would be in the 22nd century, but seemingly to overlap previous series that apparently take place in the 22nd century (either originally or through retcons). For example, as for when Classic DOOM series takes place in its respective universe see Doom Timeline and Doom Retcon Timeline (with original interpretation that they took place in 21st century and later retcons implying they took place in the 22nd century).

In general there is too much overlap for events of classic DOOM to take place in the same universe as Reboot DOOM series if they are both in the 22nd century. Although it is roughly possible that if DOOM 3 events are ignored the 21st century timeline could be the past of the Doom 2016 universe taking place century before Doom 2016 (see Worlds and Time). It would have to be assumed original military/industrial UAC evolved into the cult-like UAC over the century.

If Classic Doom takes place in the same universe as Doom 3 (either as a prequel in the 21st century or retconned as a sequel in the 22nd), Doom Reboot universe would have to be entirely seperate and parallel as it overlaps with many of the dates of Doom 3, and UAC's more cultic nature does not fit with the more scientific nature of Doom 3's UAC. Though it might be possible that instead of classic doom taking place in 2022 (it would have to be closer to 2040 as per the Art of Doom's date for when UAC started planning Mars Base).

It's less likely that if classic series took place in 22nd century since it too would overlap with the events of Doom (2016), and its history (and it seems "Our Hero'" had been hell for perpetually for a very long time according to The Lost Levels, Doom (2016), and Doom Eternal).

Regardless of which interpretations are believed, some kind of parallel universe and time travel does appear to be in place, see Worlds and Time. This timeline only covers the dates relevant and mentioned in the Reboot series (as there is no clear indication how it interacts with events of Doom 64, and when the date of that event took place, or what universe it took place in, in this reboot). Doom 64 is mentioned as a foot note...

Another theory is that Doom Reboot universe might take place in the future of the MachineGames Wolfenstein Reboot universe (long after the Nazis were defeated in the 1960-1980s, but also explaining the continued existence of cult influence in business and entertainment in the world of the reboot games).

Doom 64
21st or 22nd century (parallel universe, or dated to AE (Ancient Era calendar))?
 * Doom 64 ends: The Doom Marine enters hell one more time and vows to fight demons for eternity to prevent them from invading earth again.


 * The Lost Levels: The sister Resurrector decides to take revenge on the Marine, sending him back to Earth. He fights his way through a UAC base to find a portal back to Hell, fighting his way through the new patch of Hell he finds the Mother Demon's sister again, and takes takes revenge on her. After her defeat he again decides to remain in hell walking the perpetual path through Doom.


 * He is discovered injured by the Night Sentinels who nurse him back to health and make him their Champion.
 * Worlds and Time

Ages

 * First age
 * Second age
 * Third age
 * Fourth age

Doom 2016
''Note: Most of these dates are also listed with the designation "MTC". This is a reference to "Coordinated Mars Time".  Some additional dates appears in The Art of Doom'', some of these dates appear to be from earlier concepts and in some cases shifted about in the final game see below.
 * 80 million years ago.
 * 60 million years ago.
 * 21st Century
 * Early; Water is discovered on Mars. Very little happens in way of colonization, except exploration over the next century.
 * Late; Advanced Rocket Launcher is developed.
 * c. 2019 (assumed date)
 * Samuel Hayden is born.
 * 2095
 * The Argent Fracture is discovered. Argent plasma was discovered in a trench on Mars by an expedition from the SS Amundsen.
 * MTC 2096
 * The Union Aerospace Corporation established an outpost on Mars to extract Argent plasma from the Argent Fracture.
 * MTC 2122
 * March 10 - A statue of the Praetor Suit was excavated (Artifact U9) from Site 3.
 * MTC 2124
 * November 16 - Two Ancient Sentinel statues were excavated (Artifact J46) from Site 1.
 * MTC 2127
 * The Argent Tower is completed.
 * 6 Months Later - Samuel Hayden transfers his mind over to a cyborg body to continue his existence, after his body breaks down due to Stage 4 Cancer.
 * MTC 2136
 * The Advanced Research Complex is completed.
 * MTC 2143
 * During one of the first teleporter explorations, the Corrax tablets are retrieved from Hell in a UAC Automated Survey.
 * MTC 2145
 * 128 - The first Project Lazarus Manned Expedition is sent to Hell. The expedition ends with complete loss of human life, but achieved its mission. The sarcophagus of the Doom Marine is recovered from Kadingir Sanctum.
 * MTC 2146
 * Industrial accident related deaths in the Foundry dropped significantly thanks to new UAC safety protocols where employees exposed to dangerous materials are sent to the Lazarus Labs.
 * 351
 * The first Project Lazarus Tethering Operation is conducted.
 * Pinkies are discovered for the first time.
 * The "vade mecum" compendium is recovered from the Umbral Plains containing information on the Aranea Imperatrix.
 * MTC 2147
 * 016 - The second Project Lazarus Tethering Operation is conducted. The expedition ends in an confrontation with the Hell Guard.
 * MTC 2148
 * 177 - The second Project Lazarus Manned Expedition is sent to the Great Steppe. The expedition ends with similar losses. The petrified remains of a Baalgar demon is recovered.
 * MTC 2149
 * c. February - The Argent Facility - UAC base had its last accident.
 * October - Doom 2016 Begins.
 * December - Indentured servants on the offworld Tei Tenga Mining Station were replaced with robotic workers, optimal output expected to return to normal by this date.
 * MTC 2150
 * MTC 2151
 * MTC 2163
 * Doom Eternal begins...

Art of Doom (2016)
The Art of Doom has an early version of the timeline from the game its included here for comparison. Note: The book also mentions "AE" designation along with the "MTC" designation but there is no explanation (it is used for the 1366 date, and just talks about it being in Argent Records/UAC Archival Research, and appears to related to being an era 'over two millenia ago').


 * C. MTC 149 (AE/:1366/88)- First recorded trans-dimensional encounters with demons and humans apparently on Earth. First time demonic races were documented by humans (this may also be associated with Argent D'nur?).
 * MTC 2049 - Plans for the colonization of Mars begins. UAC, Mixom and I/O Logistics lay down the foundation of a new civilization on Mars.
 * MTC 2100
 * 000 - Early tethering operations firsthand discover possibility of species-demon hierarchy.
 * 2115 - A region known as the Well is discovered on Mars.
 * 2117 - Argent facility construction.
 * 2127 - Argent facility is completed on Mars. Samuel Hayden dies.
 * MTC 2136 - Advanced Weaponry Division is completed.
 * 2143 - UAC automated survey.
 * 2144 - Early manned UAC Expedition to Hell.
 * 2145 -
 * MTC 2146 -
 * 118 - Twins demon is discovered.
 * 351 - Pinkies discovered.
 * 385
 * MTC 2147
 * 016 - They recover a hell warden.
 * MTC 2148
 * 139 - Doomed UAC Trans-Dimensional Expedition most of the explorers were set upon by Barons of Hell.

Behind the scenes
It was theorized that the new series was a soft reboot back when Doom (2016) came out, many theorized that Doom 64 was a direct prequel to the game (but took place in aother era or paralle universe). Many believed it starred the same protagonist from all the previous games.

This was later implied withi Quake Champions where Doom Slayer was said to have owned the pet rabbit Daisy at one time, and it talks about his previous armors. It was also hinted in the game itself, in the Slayer Testements which talked about him traveling between Worlds and Time (but it was unclear if this meant 'time on earth' and alternate earths or just worlds like Hell and Argent D'nur).

Like the game Quake Champins repeated the information from Slayer Testaments with additional information. That Doom Slayer (codenamed: Doom, B.J. Blazkowicz in some contexts) was the hero of earlier Doom games (and descendent of the heroes of Wolfenstein and Commander Keen) traveled across Worlds and Time.

Regardless of if the game takes place in the 22nd century or 4th millenium. In the gams, the UAC seems to be less a industralized corporation (with some corruption), but more of a cultic religious organization (which demanded that its employees be devout worshippers of Hell), with various ranks based on its priestly devotion (whether this was something only top officials knew about, or tricked down to basic civilians is less clear), or perhaps its something introduced into the UAC in the last few years of its existence (there is no indication of it in previous games Doom 3, Doom 1, or Doom 2, etc, except maybe a few individuals who turn out to be the enemies).

The developers have since confirmed Doom 64 being the direct prequel to Doom 2016, releasing the game (as a preorder bonus) with an extra campaign The Lost Levels which makes a reference to a quote from the Slayer Testament (to link the two together). It's also explained that Doom Slayer was once human, but he has been 'enhanced' since then.