Appendix B is an annotated timeline, essentially, recapping all of Appendix A and putting the various events in order with one another. We learn that Sauron crafted the Rings of Power in the middle of the Second Age, around the same time as when the Elves and the Numenoreans were teaming up to drive him back. We learn that the Wizards (Gandalf, Saruman, Radagast, and two others) arrived in Middle Earth around a thousand years after the Last Alliance, after the civil wars in Arnor (TA 861) and before the westward migration of the Hobbits (circa TA 1150) but long after Arwen’s birth (in TA 241). When Gandalf first comes to Middle-Earth, one of the first folks he talks to is Cirdan, the Shipwright, who immediately presents him with one of the three Elf-rings, the Ring of Fire. The balrog appears in Moria at about the same time that the last King of Gondor is foolishly slain, and rule passes to the Stewards. And so on.
The timeline passes onwards and includes the events of the Hobbit and of the War of the Ring, and identifies 10 March TA 3019 as the day the sun didn’t come up, what with Sauron’s evil. And just so we’re clear, the day the attack on Helm’s Deep was lifted was the same day that Gollum betrayed Frodo to Shelob. Tremendously significant, I’m sure.
In other news, Lorien was assaulted on three separate occasions after Frodo left it and before the Ring was destroyed. After the war ended and the shadow was finally lifted from Mirkwood, Celeborn (Galadriel’s husband) and Thranduil (Legolas’s father) divided up Mirkwood between them, in northern and southern halves, but after Galadriel abandoned Middle-Earth to sail west, Celeborn realized there was no reason for him to stick around either.
Dain and Brand actually lost their battle, and both died, but they bought time for their soldiers to retreat into Erebor and seal it up, and they held out under the siege until the Ring was destroyed. Then Bard II, Brand’s son, became king, and Thorin III, Dain’s son, became the other king, and were allied with Gondor.
Then there’s an adorable little timeline about the later life of Merry, Pippin, and Sam, starting with Frodo passing westward over the sea. Sam has a bunch of kids and grandkids and is elected Mayor of Hobbiton, Merry may or may not have kids but becomes Master of Buckland, and Pippin becomes Thain of the Shire and has a bunch of kids. Some of Sam’s kids and some of Pippin’s kids marry and have more kids. Eventually Aragorn has the Shire expanded, adding a sizable chunk of land to the west of it, and one of Sam’s sons-in-law becomes the Warden there.
Sixty years after Frodo left, Sam’s wife died and within three months he said farewell to his kids, abandoned the Shire, rode out to the Havens, and got on the next boat West. At about the same time, Eomer (then super old) sent word to Merry, asking him to visit, which he and Pippin did. They arrived in Rohan to find Eomer on his deathbed, and paid their respects. Afterwards they did not return to the Shire but retired to Gondor, where they passed away.
Sixty years after that, Aragorn died of old age. Merry and Pippin’s tombs were moved into the same crypt as his. Legolas was living in northern Mirkwood at the time, but when he heard about it he built a ship, and sailed along the Anduin to Rohan. There he picked up Gimli, and the two of them sailed off to the West together.