Talk:Timeline of the Half-Life and Portal universe

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Not convinced about this page. What does everyone else think? Coming Second 16:16, 7 February 2008 (UTC)

This is basically just an outdated copy of the Half-Life Saga Story Guide's timeline. So even if we do keep it it'll need updating. Also, did whoever put this up get permission from it's creator? I don't think we have any way of knowing.

I vote we delete it. --MattyDienhoff 04:35, 8 February 2008 (UTC)

Aaargh. Despite a lot of people's best efforts, this is still terribly written and laid out. Just thinking about editing it into some sort of shape depresses me, so this is a vote for deletion. Coming Second 16:10, 4 November 2008 (UTC)
Nobody asks me stuff anymore, lolz, I vote delete, sorry dude that wrote this. -- Mega Sean 45 1:57 PM, November 4, 2008 (UTC)

Localized Teleport Technology...[edit]

The timeline, in the 20 year gap, makes no reference to the 'cat incident' or the localized teleport tech kleiner developed, removing the need for the xen relay. There's not a particular time frame mentioned, Barney just says "not after last time", but I still think it warrants a mention. 04:59, March 2, 2010 (UTC)gildedlink

Added. Do you have issues with signing?... Klow 11:13, March 2, 2010 (UTC)

Black Mesa Incident and GLaDOS' takeover dates revealed?[edit]

Gameinformer, continuing with their Portal 2 supplement this month, just released a timeline of Aperture Science. While seemingly old information at first glance, it altered some of the dates, and most notably of all, may have revealed the date for which the events of the original Half-Life occurred. It states:

"1998 – The untested AI is activated for the first time as one of the planned activities on Aperture’s first annual bring-your-daughter-to-work day. In many ways, the initial test goes well: Within one picosecond of being switched on, GLaDOS becomes self-aware. The "going well" phase lasts for two more picoseconds, at which point GLaDOS takes control of the facility, locks everyone inside, and begins a permanent cycle of testing. Her goal: beat the hated Black Mesa in the race to develop a functioning portal technology. Days later, that race is lost when Black Mesa successfully deploys an interdimensional gate through which an alien race emerges and effectively ends the outside world."

If this is true, and it seems Gameinformer are getting info more or less straight from Valve, is this not one gigantic retcon? For years it has been accepted that the events of Half-Life take place on May 16 between 2000 and 2009, but Gameinformer now states that it was 1998, days after GLaDOS' takeover of Aperture Labs. Whether a mistake or genuine, I know we should wait for confirmation from Valve, but I thought I'd point out this potentially huge revelation. The full supplement may be seen here: Aperture Science: A History. - Halo-343 22:59, March 24, 2010 (UTC)

Placing HL from 2000 to 2009 could place it in 2000, which is only 2 years after 1998, so it's actually not that far. And if that date is actually directly from Valve, this is INDEED awesome, as we can now put HL2 around 2018, and deduce the birth dates of several HL1 series characters, for instance Gordon who'd be born around 1971. However it's not very original to choose the same date as the game release date, imho. They could have chosen a bit earlier or later. And of course we should be sure it's true before jumping to gun, but I'm afraid Valve might never confirm this. But the article introduction really suggests this is all from them. Klow 23:41, March 24, 2010 (UTC)
I just checked, unfortunately it hasn't been updated with that new paragraph. Klow 23:44, March 24, 2010 (UTC)
I felt like asking the validity of that new paragraph directly to the lady who posted the article. Since she gives many contact ways, I chose the Facebook way. She was kind enough to answer me 11 minutes later this: "Nope! All of that information, aside from the introduction, was supplied directly from Valve! Hope that helps!". So, there you go, this is real. We can now unleash this huge retcon through the wiki. :-P Klow 00:30, March 25, 2010 (UTC)
On the contrary however, a couple people over at Steam Forums have emailed valved about this, and received the response "There's no way it could have taken place in the Nineties, since Gordon didn't start at Black Mesa until sometime in the Noughties!"[1][2] from Marc Laidlaw.Mr. Someguy 04:15, April 10, 2010 (UTC)
I wrote to Marc yesterday, and he told me the same. We are more or less back to square 1; we'll correct it soon on the wiki. Klow 09:08, April 10, 2010 (UTC)
I hope so! But its indeed very strange, Gameinformer has questionable sources.. -- 08:45, April 23, 2010 (UTC)

Portal Setting[edit]

Since I'm not like listening to 18 minutes of boring speech, please find and "copy" a quote where the Portal setting is in the Portal 2 podcast to me. ASBusinessMagnet 16:09, March 28, 2010 (UTC)

Just listen to it like everybody else. And I've listened to more boring stuff. Klow 16:49, March 28, 2010 (UTC)
Thanks, I found it. They weren't saying that they assume Portal takes place after Half-Life 2, they just said that it does.
I posted that because on mAL I heard that they actually aren't sure of it, and that would criticize this timeline. ASBusinessMagnet 17:06, March 28, 2010 (UTC)
Don't worry, we made sure they stated it or suggested it before jumping the gun. Klow 17:39, March 28, 2010 (UTC)
Just saying that apparently, the real quote is:
The first Portal takes place sometime after some of the events in Half-Life 2, but [some Portal 2 stuff goes here]
That means it happens simultaneously with Half-Life 2. ASBusinessMagnet 17:47, March 28, 2010 (UTC)
Then he says that it's maybe a year later. Klow 19:28, March 28, 2010 (UTC)
Something tells me that even Valve haven't thought it through this much. Only the fans really want to know when it is... Bramblepath 20:10, March 28, 2010 (UTC)


I think that adding separates sections for the 1970's, 80's, etc. is redundant, and it overcomplicated the article. I just think it should be as neat as possible. --Fireman V2 19:15, April 18, 2010 (UTC)

It doesn't overcomplicate. There can be a more logical way than to clearly separate every decade. Klow 08:31, April 19, 2010 (UTC)

Retroactive Continuity[edit]

Is listing all the retcons really needed? Could we maybe just link people to the retcons page? I'm not saying we should, just asking if it'sa good idea. -- 19:32, May 7, 2010 (UTC)

We really list a few rectons here. — Unsigned comment by Klow
What about sticking to the timeline that can be found from the game? Would that solve anything?-- 23:53, April 28, 2011 (UTC)
Combine the timelines. Assume some events repeat. History kinda does that all the time. Retcons are the last refuge of the unimaginative.ChrisMathers3501 15:11, August 19, 2011 (UTC)

7 Hour War Month[edit]

Analysis of a newspaper clipping indicates that the 7 hour war took place in September, with the main note being that the month has a P in the second to last character position. (44, 2001 is arbitrary just to demonstrate the likeness). Another point of interest is that the day appears to be two digits long.

Also, the date format is inconsistent with a typical 200_ THE TIMES newspaper, as well as the entire front-page layout: This suggests that the date is some time after November 16, 2004 (HL2 release date), allowing for THE TIMES in-game to have changed their format after that date. — Unsigned comment by

300 years between Portal and Portal 2[edit]

I've heard that 300 years separate Portal and Portal 2, can anyone confirm it? ASBusinessMagnet 22:30, April 16, 2011 (UTC)

Actually, I believe this is the Announcer bugging: "you have been in suspension for nine nine nine nine nine (bugs out)" 99999 days = 273.8 years. ASBusinessMagnet 07:34, April 19, 2011 (UTC)
Was Valve "bugging," too? I believe they said the same thing, too.

GLaDOS says in Portal 2 (this is paraphrased) "You know the old formula. Comedy=Tragedy+time. And even though things aren't going well, you've been in stasis for almost 3 centuries"

Timeline Redo[edit]

Since Portal 2 came out and retconed everything, a lot of dates need to be changed. Aperture was founded before or during 1943, went from shower curtains to actual science by 1947, had a working portal device by 1952, and Cave Johnson died between 1981 and 1986. signed a random user whos gonna get yelled at for not signing in 8:40, April 21, 2011

Also, he apparently died from meteorite dust and not mercury poisoning. Webrunner 16:02, April 23, 2011 (UTC)

Cave Johnson Moon Rock Poisoning[edit]

During the game [Portal 2] towards the last of the "Old Aperture" Cave Johnson states himself that he was poisoned due to the grounding of Moon Rock into Gel, not mercury poisoning as stated in the wiki.

While this IS true, It has been stated Long before Portal 2 that Cave Johnson had contracted mercury poisoning from one of his shower curtain ideas. One of the symptoms of mercury poisoning is neuropsychiatric symptoms, Such as memory loss, Delusions and insomina. Or in Johnsons case, Thinking time flows backwards.

I say both are possible. Think of it like this. He gets mercury poisoning, then his kidneys shut down, he starts suffering the effects of the poison, and dying. This is a long, slow painful process. Then he gets moon rock poisoning, his kidneys shut down AGAIN, and now he's dying faster. In the little time that he has left, he goes on a combustible lemon rant and lays out his plan to put a consciousness into a computer. The story is confusing enough without going back and rewriting over every date, place and event.ChrisMathers3501 15:08, August 19, 2011 (UTC)
Or, since owning moon rocks is illegal, the Mercury Poisoning was the public reason. 01:55, 25 June 2012 (UTC)

New portal 2 dates don't work with a lot of the old stuff....[edit]

I was looking at the trophy case in Portal 2 and Cave Johnson was awarded "Shower Curtain Salesman of 1943"; Aperture Science was awarded "Best New Science Company" by Science and Business Institute of America" and also awarded "Top 100 Applied Science Companies" by Mechanical Engineering World Journal in 1949. Knowing that the dates, old and new, came form Valve, how is this possible??

I'd assume that from now on we'll use the new dates and disregard the old ones. They're too contradictory to be able to coexist. SirMango 20:10, April 21, 2011 (UTC)
Is there a reason why dates like "1973: aperture is only producing shower curtains" When in game evidence shows that these are wrong. SajuukKhar 12:28, April 28, 2011 (UTC)

It didn't say "only." It said "mostly." That still works.ChrisMathers3501 15:03, August 19, 2011 (UTC)


The people over at this thread have made a good timeline based off of all the new portal 2 info. it would help with fixing timeline errors.

Placement of Portal 2[edit]

What is the basis for Portal 2 being during the Half-life 2 events when Valve has pretty well confirmed Portal 2 takes place over 200 years after Portal 1?

I don't know, Valve is pretty much baseless on timeline issues. Last time I heard The Final Hour of Portal 2 mentioned Portal 2 takes place in 52,000 AD, which is WAY beyond acceptable limits. ASBusinessMagnet 14:38, April 27, 2011 (UTC)

Bring your Cat To Work Day[edit]

Does everyone seem to forget that the Lab Rat comic shows Glados's takeover was on Bring Your Cat To Work Day and not Bring Your Daughter to work Day. SajuukKhar 14:53, April 26, 2011 (UTC)

Actually, Glados Mentions "Bring Your Cat To Work Day" After her activation and locking down the facility, Since she states "Since the Installation of my new Morality Core,..." Which was only installed after she was activated. Sorry to shoot down your theory.

Goes back and rereads comic. Hmm Glados talks about BYCTWD before shes killed everyone so.... If it was after she took over why are all the scientists acting super chill about her locking down the facility and going on with their normal day Oh and not dead. One would expect that they would all be freaking out or dead. Also can ou explain why a DoD contractor that got billions in funding every year was left to rot from like 1993 to 2003 when the BMI occurred. SajuukKhar 08:36, April 28, 2011 (UTC)

Portal 2 Date[edit]

When playing the prologue of Portal 2 with closed captioning on, it says "nine nine nine nine nine ni-," implying at least 2739 years have passed since the previous time awoken. 00:46, April 28, 2011 (UTC)

I don't think we can assume that all the nines refer to any specific amount of time. It's possibly just because the computer is malfunctioning. Insisting on a connection to any specific amount of time is really just speculation.MattyG7 06:15, April 28, 2011 (UTC)

  • The Devs themselves have said it takes place around 300 years after Portal 1 how about takeing the people who make the games word instead? 20:52, May 19, 2011 (UTC)

Portal '98 date is wrong[edit]

About the repulsion gel as a dieting aid: -- 23:52, April 28, 2011 (UTC)

Proposal: Discredit as a source[edit]

I think at this point is no longer a reliable source given (A) Portal 2 has retconned pretty much everything, and (B) it isn't a source anymore at all. Valve isn't granting access to the tier3 login interface anymore - instead you get treated to an animated Christmas scene. That seems to me to indicate that they want you to play Portal 2 to get Aperture's history. GregBFM 07:45, May 9, 2011 (UTC)

Portal 2 - the final hours[edit]

In this ebook, it was mentioned that the first Portal plays around the year 2010, which gives us a pretty good date to work with in the timeline. I just added it to the article very crudely, but I am no Wiki master (hell, I don't even have an account here) so I made a mess off of it. Someone, please clean it up.


Since when did Portal take place shortally after the 7 hour war. Didn't it take place shortally after the begining Half-life 2? If it didn't, Show me HARD PROOF from Valve. If there is none, then it's spectualation. Just pointing out something that I thought was Odd.Nurse Barbra 22:43, May 18, 2011 (UTC)

Nope, HL2 takes place in the 2020's while Portal takes place around 2010. I don't know the proof that HL2 takes place in 202- but Portal was said to be 2010 in Portal 2 - the final hours. .Wolfos

HL2 taking place in 202- is sourced in the article. "Gordon emerges from the darkness, nearly two decades removed from his last conscious thought." Here. HL1 is set in 200-, do the math. We chose dating that way for convenience. Valve will never give any dates anyway. ;) Klow 18:56, May 19, 2011 (UTC)

While I do know that Klow, I was asking for reference to the artical of "When Portal Takes Place", I already knew The BMI took place in 200- and HL2 took place in 202-, So thanks Wolfos, I just got "The final hours" on steam so this has been fixed in my mind. Thanks. Nurse Barbra 22:01, May 19, 2011 (UTC)

You got a reason for undoing my revisions, partner?[edit]

I made an edit to this page that reflected what was actually in the Opposing Force manual, allowing for the possibility that what it said doesn't need an unnecessary retcon to fit into the established continuity, NOT what somebody THINKS it should say. ChrisMathers3501 14:59, August 19, 2011 (UTC)

Canonicity of Perpetual Testing Initiative[edit]

While map editor itself is non-canon (obviously), when you play community map, we can hear Cave talking at beginning of each chamber. Doesn't this should be part of canon? If so, it should be added to timeline. If you look at trailer, you can see "ⓒ1988 All Right Reserved". It means the orientation video (Which named 'Aperture Science Extra-Earth Outsourcing and Perpetual Testing Initiative Employee Orientation Video' in-game) and usage of Multiverse by Aperture occurred at least in 1988. Dr. Kevin Joan Rattman 19:06, 18 May 2012 (UTC)

200- and Speculation[edit]

As per [3]. It seems to me that much of the evidence surrounding the HECU training, Gordon's start date, the Hazard Course timetable and the Resonance Cascade itself are victim of fan confusion, speculation and retcon. Specifically, the assumption that the incident takes place in May appears to have led to earlier dates being retconned back. — Unsigned comment by

I have already adjusted the completely fan-fabricated dates and other wild speculation and made sure the introduction clearly states Valve's stance on defining a timeline and its inherent unreliability. The Half-Life Wikia appears to still be using the wildly speculative dates, but that's just another reason why the Wikia isn't a sensibly moderated or reliable source.
As for the date of the resonance cascade, the PS2 port of Half-Life is very unambiguous about it occurring on the same day Gordon performed his HEV suit training which is definitively known to be May 16. The fabled December calendar texture is largely pure gibberish and never implied to be an actual indication of the current date (rather, it was likely thrown together by an artist without regard to accuracy to the plot as it's just a nearly illegible background detail). Yes, the May 16 date for the resonance cascade does conflict with Laidlaw's statement that it didn't happen on Gordon's first day at work (although it's never stated to be his first day either, something I will correct right now), but that is explicitly noted already. This timeline article serves more as a convenient reference rather than rule as it is simply a thoroughly cited collection of every known date, contradictions and all. Marphy (talk) 00:34, 22 January 2014 (GMT)
It seems I've missed the source for the cascade occurring on the same day as Gordon's training, could you point out where I'm supposed to be looking?
We know Gordon's start date is no later than May 15, but no earlier than May 5. However, the memo to Gina from the administrator's office makes it clear that Gordon is already at Black Mesa by May 11. That puts his start date somewhere between May 5 and May 11. 11:25, 22 January 2014 (GMT)
In the PS2 port, the scientists in the new introduction area of the Hazard Course complain about their sensors not being in a working state for Gordon's training, an event scheduled for May 16. This is a reference to the same facility-wide system problems experienced again by Gordon and Barney only a short while later before the resonance cascade. The PS2 Hazard Course also makes a point to establish that Gordon's training begins at 7:30 A.M., a deliberate choice to fit with the later known time of 8:47 A.M. during Gordon's tram ride to Sector C Test Labs. Additionally, this coincides with Barney's transfer to Blue Shift which is stated to begin on May 15 and last until August 15. We know Barney is supposed to be well into the early stages, if not the very beginning, of this assignment as a security guard at the front desk of the Area 3 Medium Security Facilities remarks to him "Hope you're ready for a long shift." Hence, May 16 fits as being among his first days of duty on Blue Shift.
Gearbox was responsible for identifying much of these dates here, so it's no coincidence the given information all closely links together. They were very meticulous with creating a cohesive storyline among their expansions that also conformed rigidly with the few known facts imparted by Laidlaw at the time. That Half-Life 2 and later episodes vaguely suggested Gordon may have worked at Black Mesa for a longer period (although, by Dr. Breen's own words, still a "brief tenure") is something Gearbox could not account for at the time and a potential inconsistency appropriately noted in the article. Marphy (talk) 12:27, 22 January 2014 (GMT)
Aah, I see. It's not exactly conclusive evidence, but it's a little too convenient to be coincidence. Everything does indeed work as-is, I'll head back to the other wiki and set to overhauling their article. 16:09, 22 January 2014 (GMT) / Portal 2 Guide / Portal 2 awards[edit]

What is wrong with these dates? Every source presents another version of history. I guess we should stick to the Portal 2 Guide as and the Gameinformer timelines come from before Portal 2 release, but even then the dates don't match with the ones given in the lobby.

The Guide, and every other source, says that Aperture Science was founded in 1953. What about the salt mine purchase in 1944? And the Shower Curtains Salesman of the year 1943? Renaming the company to "Aperture Science" in 1947?

Mercury poisoning? I guess that it speaks for itself that all the info there is outdated and comes from before some kind of redesign of the Portal timeline.

Am I missing something? Please, help! :( Pixeled sandvich.png18 (Commentary node transparent.png) 16:43, 22 April 2014 (BST)

Black Mesa Destruction Date[edit]

I have noticed the wiki claims the destruction of Black Mesa takes place on May 17. Meaning the entire Half Life 1 series spans only two days. This is almost certainly false, because Opposing Force starts on the evening of May 17 (I am placing the starting point around the time Adrian wakes up from unconsciousness), with a dim orange coloured sky. From Chapter 5 through 9, the entire game is underground, and this takes up about half the game. Once Adrian reemerges to the surface in Chapter 10, the skybox is different, but it is again dim with a somewhat pinkish hue this time. I assume a lot of people misinterpreted this as it being dusk. However, I am absolutely certain it is actually dawn, and Adrian's time below ground must have taken place over night. Considering that Opposing Force takes approximately 6-12 hours to complete according to, the entire game could not have taken place on the same day, even if we assume the events all played out in real time, as that would put the end of the game around midnight at least.

You can prove it for yourself. Once the player nears the end, they go back underground leading to the inevitable boss fight with the Gene Worm. After the fight, they are teleported by the G-Man to an escaping V22 Osprey still near Black Mesa minutes before the Nuke detonates. Looking out the helicopter shows that the skies are now bright blue with white clouds. Based on the shadows of the skybox, the sun is almost directly overhead, putting the time around midday. So it has clearly transitioned from dawn to midday. If the entire game took place over the course of May 17, it would have transitioned to night time by the end of the game. This means the actual date of Black Mesa's destruction is May 18, not May 17.

Tell me what you guys think. I don't believe this contradicts with any official sources from Valve or Gearbox that I have found so far. xxFalconArasxx 11:11, 28 May 2018 (GMT)

Trying to piece together the timeline based solely on the skybox textures is troublesome due to a lack of consistency and some flat out errors in the mapping. The opening levels of Opposing Force (after Adrian regains consciousness) look like they're intended to be the early dawn of the second day, May 17, at sunrise, but the skybox texture used in those levels is named "dusk". You argue that this must be the end of the second day which would be supported by the "dusk" skybox name, but that is false because we know OpFor's Missing In Action chapter occurs at roughly the same time as Half-Life's Surface Tension in which we see the part where the military commander orders Cooper to call in airstrikes. Surface Tension is definitely only part way through the second day of the incident since, not too long before, Gordon had just woken up earlier in the morning for Residue Processing, and the sun is out for the remainder of HL1.
As far as other coincident timings between the games, we know HL1's Lambda Core still takes place during the day as, at the beginning of OpFor's We Are Not Alone chapter when Adrian enters the Lambda teleporter room right before Gordon jumps in, Adrian had moments before saw that it was still sunny outside after rescuing the Engineer.
In regards to flat out errors, in OpFor, the map lighting at the Garg showdown on the dam in Foxtrot Uniform implies the level is meant to be at dusk, yet the map uses the normal mid-day "desert" skybox. Previous and subsequent maps to this level use the "dusk" skybox.
In general, the skybox texture progression in OpFor after Adrian regains consciousness seems to imply morning ("dusk" skybox), afternoon ("desert" skybox), and finally evening ("dusk" skybox again), thus accounting for one full day, that being the second day of the incident aka May 17. The skybox used in the concluding Osprey scene with the G-Man does show what appears to be the afternoon "cliff" skybox texture, but the texture itself is simply named "hack", a reference to the special effect of rendering multiple different skyboxes within a single map. Hence, we can't judge the time of day based on the skybox's name alone (nor is this a reliable indicator in other instances either). Nonetheless, that it appears to be afternoon after the previously seen dusk of May 17 would imply that Osprey scene and therefore Black Mesa's nuclear destruction takes place on the subsequent May 18th. That seems like a reasonable deduction, but the truth is, we don't know how literal to take these G-Man scenes. OpFor's ending is played out in a surreal manner akin to HL1's ending, and even Marc Laidlaw is ambiguous as to how consequential the visuals there were (see this email, noting he says it "verges on hallucination").
Of course, we know that Black Mesa's destruction by the thermonuclear device unambiguously occurred, but the question at hand is how many details we can ascertain about its date. Our only clue is OpFor's ending, and that tells us it could be the following day (May 18), but the way Adrian sees it could simply be an abstract illusion brought on by the G-Man. Alternatively, it could even be that Gearbox simply copied the same lighting and skybox settings from the intro Osprey cutscene to make it an obvious bookend to the whole game, thus there was no real thought behind accurately depicting the time of day.
In short, the major events of Opposing Force do conclusively and demonstrably take place over the course of May 17. The date of Black Mesa's destruction is unclear. I don't see clear evidence to declare it as being the following May 18th as our only evidence to such can't conclusively be considered literal. As for what this means as to the current wiki page, I think this at most warrants a footnote which I've added just now. Marphy (talk) 11:21, 29 May 2018 (MSK)
Pretty interesting hypothesis. Considering that Shepard does spend a lot of time below ground in the aforementioned chapters, it is entirely plausible that a night may have passed. Of course, we cannot really say for sure, unless we see this transition for ourselves in game. It would also be impossible to differentiate dusk from dawn in this game, since dusk and dawn would look pretty much the same. The only difference would be the position of the sun, and none of the skyboxes in Opposing Force have a visible sun. Now yes, the ending does appear to take place during midday, which would imply that the events after Chapter 9 took place in the morning, putting the date of detonation on May 18th, but the skyboxes in this game are very inconsistent. The game only really uses like three different skyboxes. In earlier parts of the game (before the chapters you mentioned), it is a rusty orange hue, and in later areas (after the chapters), it is a pinkish hue. There are a few times where a bluish sky is used, which could be interpreted as being around midday, morning, or evening. The placement of these blueish skyboxes are erratic though. There are about four points in the game where the blue sky is used. Once at the beginning of the game, where you are in a helicopter. Once in Friendly Fire, where you rescue the wounded engineer. Once at Foxtrot Uniform, where you encounter the Gargantua at the dam. And once at the ending of the game, where G-Man takes you to a helicopter before the nuke detonates.
So basically, here is how time is presented to us in the game... We transition from bright blue skies, to dim orange skies at the beginning, so it appears to be evening. It then transitions to bright blue skies again when we meet the wounded engineer, so I guess we went back in time. We then go down below ground for a few chapters (where it may or may not have transitioned to night). We emerge to see dim pinkish skies, so it is either dawn or dusk. We reach the dam, and see blue skies yet again. After the dam, the sky turns back to pink literally seconds later. Finally we see bright blue skies for one last time as G-Man teleports us away from the Gene Worm. As you can see, Gearbox clearly did not do the best job in terms of consistency. So we cannot really be that sure about the timeline. All we know is that every chapter on the surface is somewhere around day time, and every chapter below the surface is anyone's guess. I do have a feeling there were some errors made in atleast one or more of these levels with the blue skies though. The dam especially seems so, as it goes from gloomy, to sunny, back to gloomy in a matter of minutes.
Those are my two cents. Marphy made a lot of good points here too. You are also not the first person I have seen propose the Black Mesa Incident as being a three day series of events, as opposed to two days. OWRING has a very comprehensive hour long video on YouTube where he depicts the entire history of the Black Mesa Incident on one map. He presents the events of Friendly Fire as taking place from 6-8 pm of May 17th, the events following the Pit Worm as taking place after 4 am of May 18th, and the detonation of the nuclear bomb around 10 am. OWRING's structuring does make sense with the time transition we see at the end of Opposing Force. 08:49, 30 May 2018 (EST)