This is based heavily on
Lefaym's
timeline here and
Lorannah's
timeline here, with my own compromises between them and some added information from more recent episodes and supplemental material, as well as the Tardis Wiki and
Melina123's
timeline here. I'm working on the concurrent timeline theory, which means a lot (but not all) of the printed dates we see I'm going to shift backwards by a year.
Things that apply to the Golden Age 'verse but not to canon are included in brackets.
Prehistory:
Jan 2000: Jack takes over as leader of Torchwood 3.
June 2001: Construction of Flat Holm facility begins.
2002: Ianto's father dies.
Fall 2003: Tosh is imprisoned by UNIT.
March 2004: DW101 "Rose"
Mid 2004: Ianto starts working at Torchwood 1.
Summer 2004: Jack recruits Tosh; Katie Russell falls ill.
Aug 2004: Jack meets Estelle again.
Everything to do with recruiting Tosh and Owen is fuzzy timewise; as the earlier timelines do, I'm assuming that "4 years" given in the show actually means "4 years, give or take a few months".
2005:
Feb 2005: Owen joins Torchwood 3.
March 2005: DW104/105 "Aliens of London" and "World War Three"
Spring 2005: How quickly would the (presumably special) election have gotten under way? When would Harriet have taken office? According to the UNIT website, she becomes acting PM immediately after the destruction of No. 10; is that believable?
Sept 2005: DW111 "Boomtown"
[Fall 2005: Post-CoE Jack arrives and meets with Harriet.]
Dec 2005: DW200 "The Christmas Invasion"
2006:
Early 2006: The vote of no confidence; Harold Saxon appears
Feb 2006: DW203 "School Reunion"
March 2006: DW20? "Love and Monsters"; Saxon becomes Defense Minister.
April 2006: The Ghost Shifts begin.
June 2006: DW212/DW213 "Army of Ghosts" and "Doomsday"
Everything between here and the Christmas eps is kind of squidgy, timewise, but if we go with Lefaym's timeline, we've got Ianto returning to Cardiff within a couple of weeks of Canary Wharf (Jack's attitude in "Fragments" implies to me that it was little longer) and Gwen arriving only a couple weeks later (again, it seemed to me that it had been longer). But Lorannah's timeline has Ianto arriving in June and Gwen in September, which means Ianto would be keeping Lisa secret for almost 4 months, and I don't find that believable either. So I've compromised by placing Gwen's arrival in early August. This allows Ianto and Myfanwy time to settle in and Suzie time to get obsessed with the Glove (presumably, Jack wouldn't have assigned it to her in the immediate aftermath of Canary Wharf -- they'd both have had too much to do); it also explains why Gwen missed Tommy's last resuscitation.
I've also moved "Random Shoes" up several eps. If we use the airdate order, then we've got a lot of stuff packed into a very short time, with no room for Ianto's suspension, and then nothing at all going on in November. But timeline-wise, "Random Shoes" is pretty insignificant; it gives an October date for his auction, but it doesn't affect the character arcs in any way, or impact anything else in the 'verse. Content-wise, there's no real reason this ep has to take place after "They Keep Killing Suzie". So I've decided it doesn't. This allows us to keep the auction date while allowing a little more breathing room between eps. I'm not entirely happy with this solution; I wouldn't mind switching two eps around, but having it skip three places in line is pushing it. But I don't see how we can keep both the auction date and the suspension otherwise.
I don't consider the books canon, but I'd like to think that roughly similar events occurred in our timeline; they just didn't necessarily play out the same way. "Border Princes" in particular could probably use major rewriting, but it is set in October. "Slow Decay", by publication order, is set after "Border Princes", but the content places it before "Cyberwoman".
July 2006: Ianto arrives at Torchwood 3.
Aug 2006: "Everything Changes", "Day One, "The Ghost Machine", "Another Life"
Sept 2006: "Slow Decay", "Cyberwoman", Ianto's suspension
Oct 2006: Ianto's suspension, "Small Worlds", "Random Shoes", "Border Princes"
Nov 2006: "Countrycide", "Greeks Bearing Gifts", "They Keep Killing Suzie"; Lucia Moretti dies.
Dec 2006: "Out of Time", DW300 "The Runaway Bride"
2007:
Jan 2007: "Combat", "Hidden", "Captain Jack Harkness"; Saxon's election campaign
Feb 2007: "End of Days", DW311 "Utopia"
May 2007: DW301 "Smith and Jones", DW306 "The Lazarus Experiment"; Himalayas trip
June 2007: Himalayas trip, Election Day, DW312/313 "Sound of Drums" and "Last of the Time Lords"; "Kiss Kiss Bang Bang"
July 2007: "Sleeper" and "To the Last Man"
Unknown: "Legacy of Torchwood One" (post-KKBB, pre-"Reset")
Unknown: "Everyone Says Hello"
Unknown: "Something in the Water"
Unknown: "Trace Memory" (after TTLM but before "Reset" and "Twilight Streets"?)
Unknown: "Twilight Streets" (in the fall, but before TTLM? final planning for the wedding; has cryo, so how important are the references to TTLM?)
Aug 2007: "Meat", SJA100 "Invasion of the Bane"
Unknown: "In the Shadows" (after "Twilight Streets", between "Meat" and "Adam")
Sep 2007: SJA101/102 "Revenge of the Slitheen", "Adam"
According to "Pack Animals", Owen is zombified before Halloween. Although I haven't read it yet, it sounds like "Pack Animals" takes place only shortly before "Something Borrowed." And "SkyPoint" says there's two months between Owen's death and Gwen's wedding?
Oct 2007: "Reset", "Dead Man Walking", "Day in the Death", SJA103/104 "Eye of the Gorgon", "Pack Animals"
Nov 2007: SJA105/106 "Warriors of Kudlak", "Something Borrowed"
Dec 2007: "SkyPoint" (immediately after honeymoon; simultaneous with "Plant Life") SJA107/108 "Whatever Happened to Sarah Jane", DW400 "Voyage of the Damned"
2008:
Jan 2008: "From Out of the Rain", SJA109/110 "The Lost Boy"
Feb 2008: "Adrift"
Unknown: "Jetsam" and "Rift War" (Tosh is alive, and "Rift War" takes several weeks)
March 2008: "Return of the Vostok", "Fragments"/"Exit Wounds"
April/May 2008: "Lost Souls"
June 2008: DW401 "Partners in Crime", DW404/405 "Sontaran Strategem" and "Poison Sky"
July 2008: SJA "The Last Sontaran"; DW412/413 "Stolen Earth" and "Journey's End" [Mickey joins Torchwood 3]
I'm shifting here again. "Lost Souls" clearly comes between F/EW and SE/JE, but to me it felt like only several weeks later, as opposed to the months necessary to match the real Big Bang Day. Also, there are comments to Lefaym's timeline indicating that SE might have happened in July. Since I despise what "Lost Souls" does to a wonderful real-life organization, I see no reason to hold it to the real-life timeline; with Harriet in charge, the funding and schedules might have shifted anyway.
I'm also assuming that Mickey joined Torchwood 3. He doesn't have to stay permanently, but with T3 shorthanded and Mickey having no valid identity, much less resume, back in this 'verse, it makes no sense for him to do anything BUT come to Cardiff, at least for a few months until he can get his feet back under him.
Unknown: "Almost Perfect" (after EW, no Mickey)
"Into the Silence", "Bay of the Dead"
"House That Jack Built" (immediately after "Bay of the Dead")
"Undertaker's Gift", "Risk Assessment" (which of these two came first?)
"Consequences" (five stories)
Oct 2008: SJA "Day of the Clown"
Unknown: SJA "Secrets of the Stars", "Mark of the Berserker", "Temptation of Sarah Jane", "Enemy of the Bane"
Apr 2009: DW "Planet of the Dead"
Summer 2009: "The Sin Eaters", "Asylum", "The Golden Age", "The Dead Line"
Sep 2009: "Children of Earth"
2012: "Dalek" (Diana) and "Fear Her" (Torchwood publically known)
Magazine Yearbook short stories, unknown dates:
Pre-EW: "Black Water", "Mrs Acres", "The Beauty of Our Weapons", "Plant Life", "Monster",
Pre-EW: "Harm's Way", "The Book of Jahi"
Post-EW: "Who By Fire", "Gordian"
Unknown: "The Man Who Dreamed of Stars", "Closing Time"
Comics, unknown dates: "Captain Jack and the Selkie", "Broken" (post-EW)
I really need to find out how to add a tab-space in html.