The following list is a loose representation of the planes and locations of the RD&D multiverse, associating each major part with the products that describe it. The products named inside square brackets are cited in here for being the first appearance of a location, or its most current valid description, or a description of an important point in time for that location (before major changes due to a new edition of D&D). Most of these are considered core products for each setting, but not being cited here doesn't make a supplement for these campaign settings not part of the canon; these are just starting points.
the Multiverse
fantasy Earth universe
fantasy Earth material plane
hyperspace
subspace
the Plane of Shadows
the Great Wheel [Planescape Campaign Setting, ; Manual of the Planes, ; Planar Handbook, ]
the Prime Material Plane [Spelljammer: AD&D Adventures in Space, ]
Greyspace
Oerth
Flanaess [World of Greyhawk, ; Living Greyhawk Gazetteer, ]
Mystara crystal sphere
Mystara [X1 The Isle of Dread, ; GAZ1 The Grand Duchy of Karameikos to GAZ14 The Atruaghin Clans, to ; Dawn of Emperors: Thyatis and Alphatia, ; Wrath of the Immortals, ]
Blackmoor [The First Fantasy Campaign, ; Dave Arneson's Blackmoor Campaign Setting, ]
the Known World
the Hollow World [Hollow World Campaign Set, ]
Thunder Rift []
the Savage Coast [Red Steel, ; Savage Coast Campaign Book, ]
Jakandor [Jakandor, Island of War, ; Jakandor, Isle of Destiny, ; Jakandor, Land of Legend, ]
Pelinore [Imagine magazine, ]
Krynnspace
Krynn
Ansalon [DL1 Dragons of Despair to DL16 World of Krynn, to ; Dragonlance Adventures,
Nehwon [Lankhmar – City of Adventure, 1985; Fritz Leiber's Lankhmar: The New Adventures of Fafhrd and Gray Mouser, 1996]
The current year of the RD&D campaign is 1368 DR (or 336 NR) in the Realmspace, 1523 HC in the Aebrynisspace , FY 5 in the Crimson Sphere, 382 AC in the Krynnspace, 588 CY in the Greyspace, 752 BC in the Demiplane of Dread, and 1038 AC in the Mystara crystal sphere; 5050 OC for spelljammers and 127 Ha in Sigil. These relationships between the current year in each campaign setting are tentative at the moment.
Campaign starting dates for major products
Birthright
The year is 388 days long, divided into 12 months of 4 weeks, each with 8 days, and 4 extra days.
1524 HC (551 MR, 2039 MA) — Ruins of Empire, p. 6. In Birthright Campaign Setting (1995: AD&D2R)
Dark Sun
The year is 375 days long, divided into three phases of 125 days or 25 weeks of 15 days. Years are counted in cycles of 77 named years.
190th King's Age, the Year of Priest's Defiance (Y26), High Sun (FY 1) — Rules Book, p. 85. In Dark Sun (1991: AD&D2)
190th King's Age, the Desert's Fury (Y36) (FY 11) — The Age of Heroes: Rules for Conquering the Savage Land, p. 93. In Dark Sun Campaign Setting: Expanded and Revised (1995: AD&D2R)
Dragonlance
The year is 360 days long, divided into 12 months. The day is 24 hours long. (Each of the four moons phases are 9 days for Solinari, 7 days for Nuitari, and 2 days for Luitari.)
352 AC — Dragonlance Adventures, p. 104 (1987: AD&D1)
358–369 AC — World Book of Ansalon, p. 11. In Tales of the Lance (1992: AD&D2)
415 AC (31 SC) — Dusk or Dawn: Ansalon in the Fifth Age, p. 29. In Dragonlance: Fifth Age (1996: SAGA System)
420 AC (39 SC) — Dragonlance Campaign Setting, p. 210 (2003: D&D3)
Eberron
The year is 336 days long, divided into 12 months of 4 weeks, each with 7 days. The day is 24 hours long.
998 YK — Eberron Campaign Setting, p. 225 (2004: D&D3.5)
Forgotten Realms
The year is 365 days long, divided into 12 months of 3 tendays and 5 extra days. The day is 24 hours long.
1357 DR, Nightal 30 — Cyclopedia of the Realms, p.7. In Forgotten Realms Campaign Set (1987: AD&D1)
1367 DR, Nightal — A Grand Tour of the Realms, p. 23. In Forgotten Realms Campaign Setting (1993: AD&D2; revised, 1996: AD&D2R)
1368 DR, Tarsakh, 13th — RD&D's Lost mine of Phandelver campaign
1370 DR — The Wilderness, p. 14. In The North: Guide to the Savage Frontier (1996: AD&D2R)