A coherent chronology is one of the touchstones of solid, believable world design but the Spelljammer setting has never had a coherent chronology. In part this was most likely a conscious design choice, since Spelljammer was intended not so much as a campaign setting as a campaign link, connecting all of TSR's settings together. However, it also likely came about from simple laziness on the part of some Spelljammer authors, who tended to ignore other Spelljammer material unless they wrote it themselves. Even the broad strokes of the Spelljammer universe's history are thus confused and contradictory.
It is possible to construct a generally coherent timeline for Spelljammer from references in a wide variety of sources. I have endeavored to do so, sticking strictly to published sources. The goal is to produce a timeline that Spelljammer dungeon masters can refer to when creating their own, specialized Spelljammer campaigns.
The first step in producing a coherent Spelljammer timeline is synchronizing the dating systems of the TSR settings. This is relatively difficult; it requires concrete intersection points, common events given a date in multiple worlds. Note all of the worlds have such intersection points, and several of the intersection points that do exist contradict each other.
This timeline omits the TSR settings of Birthright, Conan, Darksun, Lankhmar, Mystara, Odyssey, Planescape, Ravenloft, and Red Steel. Generally these settings have little or no connection to Spelljammer, and Spelljammer fits in their milieu very poorly.
Mystara and Red Steel have an alternative magical space travel system, but lack any direct connection to Spelljammer. There are no concrete chronological intersection points between Spelljammer and Mystara nor between Mystara and any other TSR setting, so any connection made here would be purely speculative. A dungeon master who wishes to connect Spelljammer and Mystara would be better served simply choosing a point where the settings' dating systems intersect.
Ravenloft and Planescape fill a special niche. The Demiplane of Fear, Ravenloft has no direct link to Spelljammer, but several Ravenloft novels provide specific chronological intersection points between multiple settings. Planescape novels and game products do mention Spelljammer, and they also provide some chronological intersection points across settings. Ravenloft and Planescape provide no timeline entries, but do get referenced for synchronizing the setting timelines.
The three primary TSR settings were Dragonlance, Forgotten Realms, and Greyhawk. Each of these settings had a Spelljammer sphere book produced specifically for that sphere, and each had native characters appear in Spelljammer novels, comics, and adventures. They formed the core of the Spelljammer setting. Although Kara-tur/Oriental Adventures and Al-Qadim were marketed as separate settings, they were actually regions of Toril, on the same planet as the Forgotten Realms setting. Like the Forgotten Realms they both had Spelljammer references appear in some of their products, and Kara-tur had native characters appear within Spelljammer novels and comics. The Dragonlance, Forgotten Realms, and Greyhawk settings provide the timelines that must be synchronized. Once they are linked up, the rest of the timeline begins to fall into place. This is easiest to accomplish by linking to the Forgotten Realms, since it is the setting with by far the largest number of published works, and the largest number of crossovers.
There are four sources for the chronological intersection points between the settings: Spelljammer products, Ravenloft novels, Planescape products, and Dragon magazine articles. Because the sources contradict each other in places, a hierarchy is needed to determine which source takes precedence over the others. The natural trump is Spelljammer, since the purpose here is to create a Spelljammer timeline.
The Spelljammer novel series provides us with our firmest chronological intersection point, and that point intersects the Dragonlance and Forgotten Realms settings. The first Spelljammer novel, Beyond the Moons, is set on Krynn and is clearly set five years after the end of the War of the Lance (p76). The War of the Lance ended in 352 AC according to Dragonlance Adventures (p101), but that is really the year of the Whitestone Council. Given Teldin Moore's role as a muleskinner, and the continuing operations, his war likely ended in 353 AC (which other Dragonlance products list as the end of the War of the Lance). The second Spelljammer novel, Into the Void, is a Forgotten Realms crossover and is clearly set less then a year after Beyond the Moons (pp 63,168, & 172). "Novel Ideas" Dragon #196, an article providing a chronology of Realms fiction, sets Into the Void specifically in 1361 DR (p66). From this we get 1361 DR corresponding to 358 AC.
There are contradictory sources, however. The Ravenloft timeline has Lord Soth of Krynn entering the Demiplane of Fear in 357 AC, shortly after the Blue Lady's War (Dragonlance: Fifth Age, p22). It connects this to the year 720 in the Barovian calendar of Ravenloft (Domains of Dread, p17). It also has the Forgotten Realms elven vampire Jander Sunstar drawn from the Forgotten Realms into Ravenloft in 1098 DR in the Realms, and 452 in the Barovian calendar (Domains of Dread, p16, Villain's Lorebook, p16). However, "Novel Ideas" Dragon #196 places the Forgotten Realms/Ravenloft crossover novel in 1098 DR and 475 Barovian (p65). Following the Ravenloft/Dragonlance/Forgotten Realms link we have 1361 DR corresponding to 352 or 375 AC.
The Planescape accessory On Hallowed Ground also provides a contradiction. It states that the events of the Dragonlance novel, Dragons of Summer Flame, occurred recently (p164). The novel is set in 383 AC. It also states that the Time of Troubles occurred in the Forgotten Realms just over twelve years ago (p168). The Time of Troubles was in 1358 DR, so that would link 1370 DR and 383 AC. Using this as an intersection 1361 DR would correspond to 374 AC.
We can generally discount the Ravenloft and Planescape information here, because we've already established that Spelljammer products trump other sources for the purposes of this timeline, and because we have a contradiction within the Ravenloft timeline itself. So, we can designate 1361 DR and 358 AC as our first intersection point.
A Greyhawk/Forgotten Realms chronological intersection point is more difficult to arrive at, because the Spelljammer novel series never visited Oerth, the world of the Greyhawk setting. There is a Greyhawk/Ravenloft/Forgotten Realms intersection, through the Lich Azalin. Azalin entered Ravenloft from Greyhawk in 542 of the Barovian calendar (Domains of Dread, p16) and 391 CY on Oerth (King of the Dead, ch. 18). Linked to Jander Sunstar and the Forgotten Realms as noted above, this provides 1361 DR corresponding to 564 CY.
Dragon magazine provides an alternative correspondence. Ed Greenwood wrote a series of articles about the wizards Elminster, Mordenkainen, and Dalamar meeting in his home to discuss the magical affairs of Faerun, Oerth, and Ansalon. These articles reference some specific events in relation to each other, and are internally consistent (each successive article clearly occurs subsequent to the previous article). "Magic in the Evening" Dragon #185 states that the Forgotten Realms novel The Parched Sea, which "Novel Ideas" Dragon #196 dates to 1360 DR (p66), has recently occurred. "Magic in the Evening" Dragon #185 also states that the article is set prior to Vecna Lives (p62). Vecna Lives is set in 581 CY according to The Adventure Begins (p119). This would provide us with 1360 DR corresponding to 580 CY. The next two articles in the series bolster this conclusion, "The Wizards' Three" Dragon #188 (p32) is specifically set after Vecna Lives and "Three Wizards Too Many" Dragon #196 (p84) is set specifically after the beginning of the Greyhawk Wars in 582 CY (The Adventure Begins, p119).
Support for the Dragon article correspondence comes from comparing the Greyhawk/Forgotten Realms intersection with our firm Dragonlance/Forgotten Realms intersection. "Magic in the Evening" Dragon #185 clearly implies that the War of the Lance (353 AC) and the Blue Lady's War (357 AC) have just recently occurred. If 1361 DR equals 358 AC, and 1360 DR equals 580 CY, then the first article would take place shortly after the Blue Lady's War. On Hallowed Ground does provide a specific date of 1370 DR (p168) to compare with a 'current climate of war' sweeping Oerth (p166). The Greyhawk Wars officially end in 584 CY (From the Ashes: Atlas, p9), but wars between Iuz and Furyondy, and Nyrond and the Great Kingdom essentially continued. Certainly a 'climate of war' can be said to exist across Oerth for at least a decade after the end of the Greyhawk Wars.
We have, then, two conflicting intersections, 1361 DR with 564 CY, and 1361 DR with 581 CY. The Dragon articles provide the better choice, because they were written by Ed Greenwood, the creator of the Forgotten Realms, because they were written expressly to provide setting interactions, and because they place the two settings' internal chronology more closely inline with their publication histories. We can set our second intersection point at 1361 DR and 581 CY.
With three 'firm' chronological intersection dates (1361 DR, 581 CY, & 358 AC) we can construct the timeline. However, we have to settle on a dating system. Most Forgotten Realms dates are provided in Dale Reckoning (DR), but many other systems of tallying years exist on Faerun, not to mention the lands of Kara-tur and Al-Qadim. Greyhawk likewise has several time systems, as does Dragonlance. Spelljammer products actually provide three additional systems. A chronology is easiest when a single dating system is used as the base, with others noted as needed. The elves are the current dominant power in space according Spelljammer, and Greyhawk is the oldest of TSR's settings, so the Olven calendar (OC) of Oerth will be used as the base dating system in this Spelljammer timeline.
Al-Qadim has no dating system, but Kara-tur has systems for Shou Lung, Wa, and Kozakura. The Shou system is predominant, in Kara-tur products the Wa and Kozakuran systems are described in relation to it. We lack a common event given a date on both the Dale Reckoning and Shou calendars; though the Horde Wars are copiously detailed and dated in various Forgotten Realms products, no Shou dating is providing for these events anywhere. With no intersection point, we fall back on the 'current' dates of the Kara-Tur boxed set and the original gray Forgotten Realms boxed set. This pegs 2607 of the Shou calendar to 1357 DR. This is reasonable, since the Horde Wars clearly occur within the next decade after each set.
We have three Spelljammer calendars: the Time of Unity (TU) system from SJA3 Crystal Spheres, the Anno Vulkarus/Promo Novo (AV/PV) system from SJA4 Under the Dark Fist, and the Astromundi Chronos (AC) system of the Astromundi Cluster boxed set.
We know that in 852 TU T'Laan the vampire has lived 317 years past his birth on Toril. We also know that in 1065 DR he served as an advisor to Brindor in the talks following the Battle of Ingdal's Arm. We can set the current year for Spelljammer: AD&D Adventures in Space to 5039 OC by comparing its information with the information in SJR5 Rock of Bral. Setting SJA3 Crystal Spheres to the same year is reasonable, since nothing within it indicates it occurred any later, and it came out soon after the original boxed set. This also makes T'Laan twenty-five at the Battle of Ingdal's Arm, again reasonable.
463 AV is the stated current year for SJA4 Under the Dark Fist (p51). The module provides only two clues about where it fits within the larger chronology. Based on the background of the pre-generated PCs it occurs post-War of the Lance, and the lack of mention of the Scro indicates it predates the II Unhuman War. If it is set in 5041 OC then the War of the Lance is over, yet the II Unhuman War has yet to begin in any of the major three spheres.
The Astromundi Chronos of the Astromundi Cluster boxed set is not a simple count of years. Like the Kozakuran calendar of Kara-tur it is divided into yearlong cycles. The Kozakuran calendar uses sixty-year cycles, but the Astromundi calendar uses thirteen-year cycles. The cycles are numbered, but the years are not. The Astromundi Cluster details the sphere's history until year Munigor of the 1300th cycle. Fortunately, the year names follow the same pattern; Munigor is always the second year of its cycle. We can express the AC year with a simple slash system: year/cycle. Since the system began with the First Cataclysm of the sphere, it is currently 16,889 years since the calendar began. There is no indication how the Astromundi Chronos corresponds to any other calendar, so we have to assign a current year to the Astromundi Cluster boxed set. It was printed in 1993, a year after War Captains' Companion and Rock of Bral. With no other markers, setting the current year at 5049 OC, the same as Rock of Bral makes sense.
The accepted primary dating system of Greyhawk is Common Years (CY); according to the "Brief Historical Timeline for the Flanaess" card sheet in From the Ashes 581 CY equates to 5043 OC. Therefore 5043 OC, 581 CY, 358 AC, 1361 DR, 2611 Shou, 465 AV, 856 TU, and 9/1299 AC are all now synchronized.
Of course, there are other issues which effect dating. For example, years, days, or months could be of differing lengths. For the purposes of this timeline, however, we must ignore these problems and assume one year equals one year. Otherwise the project is unfeasible.
This is not a comprehensive history of all of TSR's campaign settings. It only includes events listed in Spelljammer products, or events that had a global significance. Faerun's Time of Troubles and Krynn's Cataclysm are prime examples of the sort of non-Spelljammer related events that were considered influential enough to be included.
Comments and additions welcome. For suggested additions, please note if the said addition is from a TSR published source and if an actual date is given or if it must be inferred.
Entries are listed by year. Each entry is begun with a notation indicating the game setting it comes from (ie [SJ] = Spelljammer, [FR] = Forgotten Realms, [GH] = Greyhawk, [AQ] = Al Qadim, [DL] = Dragonlance, [KT] = Kara Tur). They are followed by the date in the world's own calendar (if not a Spelljammer only event) and a citation with the source and pagination.
* Events marked with an asterisk do not have a specific time notation but the general chronology is correct.
@ Events marked with a '@' symbol are past events with no specific time notation nor a sense of when the event occurred. These events are best guesses on my part.
c Dates preceded by a 'c' are 'circa'. Dates without the 'c' are specific.
 There are some discrepancies between the dates given in Netheril: Empire of Magic and Cormanthyr: Empire of Elves. The later is more recent, and most likely correct, but the wording of the entries allows both to be used with little conflict. The events are far in the past, and the difference between the two only fifty years, so I've simply left both within the timeline without reconciling them.
These events are dated for OC, but also for the Forgotten Realms DR and the Nether Years (NY) of the Empire of Netheril. -3859 DR equals 1 NY, according to Netheril: Empire of Magic.
 This War Captain's Companion entry is dated after the 'current date' of that work. This results from an internal inconsistency. Since having this event occur after the 'current' year of the WCC doesn't contradict anything, I left it as is.
Listed according to copyright date, with the exception of the Cloakmaster Cycle novels, which are listed as a group at the end of the Spelljammer products.
Not every entry below is cited to specific events above. If an item appears below, but has no event cited, then it provided no entries. Bibliography citations which have no timeline entries are primarily Spelljammer products, included to indicate the completeness of the research.