Timeline of the Half-Life universe

This is a timeline of the Half-Life series, gathering known dates. Several retcons having been made since the first game's release, because it is still being written as of today (April 2009), and because technological limitations have changed in the intervening time, a complete official Half-Life series timeline will probably never be made, since it could probably make the writers contradict themselves and limit their creativity for possible subsequent episodes. Despite of that, general events can be organized in a chronological order.

1953
Aperture Science begins operations as a manufacturer of shower curtains. Early product line provides a very low-tech portal between the inside and outside of your shower. Very little science is actually involved. The name is chosen to make the curtains appear more hygienic.

1956
Eisenhower administration awards Aperture a contract to provide shower curtains to all branches of the military except the Navy.

1957 - 1976
Aperture Science produces mostly shower curtains.

1970's or early 1980's
Gordon Freeman is born.

Late 1970's or 1980's
Adrian Shephard is born.

1978
Aperture Founder and CEO, Cave Johnson, is exposed to mercury while secretly developing a dangerous mercury-injected rubber sheeting from which he plans to manufacture seven deadly shower curtains to be given as gifts to each member of the House Naval Appropriations committee.

1979
Both of Cave Johnson's kidneys fail. Brain damaged, dying, and incapable of being convinced that time is not now flowing backwards, Johnson lays out a three tiered R&D program. The results, he says, will 'guarantee the continued success of Aperture Science far into the fast-approaching distant past.'

1981
Diligent Aperture engineers complete the Heimlich Counter-Maneuver and Take-A-Wish Foundation initiatives. The company announces products related to the research in a lavish, televised ceremony. These products become immediately wildly unpopular. After a string of very public choking and despondent sick child disasters, senior company officials are summoned before a Senate investigative committee. During these proceedings, an engineer mentions that some progress has been made on Tier 3, the 'man-sized ad hoc quantum tunnel through physical space with possible applications as a shower curtain.' The committee is quickly permanently recessed, and Aperture is granted an open-ended contract to secretly continue research on the 'Portal' and Heimlich Counter-Maneuver projects.

1981-1985
Work progresses on the 'Portal' project. Several high ranking Fatah personnel choke to death on lamb chunks despite the intervention of their bodyguards.

1982
This is the oldest known date of the Enrichment Center Test Subject Application being applied to Aperture Science's test subjects. Although the GLaDOS project will not start before 4 years, the prompt displays "GLaDOS v1.07 (c) 1982 Aperture Science, Inc.".

The hacker message talks about "working on twenty year old equipment". If that message was written around the time of the Portal events, that would set the game roughly in 2002, which would be the same date as the possible date for the Half-Life events.

1986
Word reaches Aperture management that another defense contractor called Black Mesa is working on a similar portal technology. In response to this news, Aperture begins developing the Genetic Lifeform and Disk Operating System (GLaDOS), an artificially intelligent research assistant and disk operating system.

1996
After a decade spent bringing the disk operating parts of GLaDOS to a state of more or less basic functionality, work begins on the Genetic Lifeform component.

Several years after 1996
The untested AI of GLaDOS is activated for the first time as one of the planned activities on Aperture's first annual bring-your-daughter-to-work day.

"200-"
This is the decade during which the Half-Life events occur.

Note about the date
Although it could range from 2000 to 2009, a note by Marc Laidlaw seen in Half-Life 2: Raising the Bar features "March 31, 2003". Although it has not been confirmed by Valve, it is possible that the Half-Life events started on March 31, 2003 and that the team decided to remove it to allow more flexibility. Also, Shephard's last journal entry (see below) is dated "March 15", the same month as this date (and 2 weeks before), which could corroborate the possible canonicity of the date. Of note is also a calendar seen at least in the Half-Life chapter Office Complex, in the Half-Life: Opposing Force chapter Welcome to Black Mesa and in the Half-Life: Blue Shift chapters Insecurity and Captive Freight), always showing the December page that should be either 2003 or 2008, given the week days arrangement. Again, even if the month contradicts other source, the date 2003 is seen again.

Adrian Shephard's journal entries
March 3

"Another typically hellish day at base camp. I'll be glad when this is over and I can finally can get assigned a mission. There has been this really weird civil spotted at the base. Rumor is he's from some government branch looking to recruit; others say he's with some secret research group. I would jump at the chance to join. It would be cool just for the change and the adventure."

March 7

"I finally saw the government guy today. I am not sure he is a g-man, but he was wearing a really uptight suit and carrying a briefcase. He looked more like a lawyer or insurance agent to me. I did notice him checking me out. Several times throughout the day I spotted him just watching me during training. I wonder what he's up to..."

March 9

"For weeks our drills have been the same crap day after day. Today we assemble for the morning run and our drill instructor tells us we have one week to become experts at indoor strategic combat. We will be spending every day this week at the combat simulation facility. As far as I know this a specialized training not taught in boot camp. What I want to know is if this is to test our ability to adapt or if we are being readied for a specific mission? Time will tell..."

March 12

"The rumors have been flying since our indoor combat training began. Most of my peers are convinced that we are being primed for a mission. No one can agree on what the mission is. I have heard the name Black Mesa Facility thrown around a lot, but I have no information about the place. The rumors are that some top-secret research is going on there. Doesn't sound too exciting to me..."

March 15

"The rumor has been confirmed. We are being trained for a mission at the Black Mesa Facility. All I know is that the place is being used by scientists who are doing some kind of new research. I can't imagine what we would be needed for. We were told today to be ready in case it happens tomorrow. I don't know what "it" is, but the whole thing is a little strange. I kind of hope it doesn't happen; the mission doesn't seem to have much excitement potential. I'd rather hold out for something with more likelihood of combat."

After March 15
At Black Mesa, physicist Gordon Freeman triggers a Resonance Cascade during an experiment gone wrong. Xen creatures teleport to Earth. Gordon Freeman, Adrian Shephard, Barney Calhoun, Colette Green and Gina Cross are fighting their way through the facility. Black Mesa is destroyed by an atomic bomb. Gordon Freeman and Adrian Shephard are placed in stasis by the G-Man while Barney Calhoun successfully escapes.

After "200-"
Portal storms continue and Xen creatures are teleported onto Earth. The governments and United Nations provide the protection centers located in major cities worldwide.

The Combine Empire launches an assault on Earth. Governments and the United Nations enter into war against the Combine. The Seven Hour War occurs. Finally, governments of the world and the United Nations who capitulate to this case, the integration of the Earth in the Combine Empire.

c. 20 years after "200-"
Gordon Freeman is awakened by the G-Man after a long period of stasis. He explores City 17 and encounters the Resistance. Soon after he joins there cause (several of his old Black Mesa colleagues are involved in it). A revolution is started (Gordon is the catalyst) and Gordon is called into stasis by the G-Man a second time after defeating Wallace Breen, Black Mesas old Administrator. He is freed from stasis soon after by a group of Vortigaunts. The Resistance gains considerable ground but unfortunately Eli Vance is killed by an Advisor soon after the Battle of White Forest, where a Combine Superportal is reversed.