The 1900s
Events of this decade:
(QA7)
1900 (Y-80) AD = 19
1901 (Y-79) AD = 20
1902 (Y-78) AD = 21
(fw)
1903 (Y-77) AD = 22
1904 (Y-76) AD = 23
1906 (Y-74) AD = 25
(BFT)
1907 (Y-73) AD = 26
(HBP13)
The 1910s
1910 (Y-70) AD = 29
1911 (Y-69) AD = 30
(fw)
1912 (Y-68) AD = 31
(BFT)
1915 (Y-65) AD = 34
(fw)
(BFT)
1917 (Y-63) AD = 36
[Frank Bryce] is bornFrank was about to celebrate his 77th birthday at the beginning of GF, which is 1994 [[Y14]]. He was born, then, 77 years before this, which is 1917 [[Y-63]].
(GF1)
1918 (Y-62) AD = 37
(FB)
1919 (Y-61) AD = 38
The 1920s
1920 (Y-60) AD = 39
(BFT)
1921 (Y-59) AD = 40
(QA7)
1922 (Y-58) AD = 41
c. 1925 (Y-55)

October 4 comes from JKR.
original artwork © 2001 [Laura Freeman], used by permission
1925 (Y-55) AD = 44 MM = 0
(BFT)
This happens "a few months" before Merope marries Tom Riddle.
(HBP10)
[Dumbledore] says that Merope and Riddle were married about a year before Tom Marvolo Riddle was born, on December 31, 1926 [[Y-54]].
(HBP10)
1926 (Y-54) AD = 45 MM = 1 TR = 0
(QA9)
Marvolo Gaunt returns from [Azkaban] to find Merope goneHe had been given a six-month sentence. Forced to live alone, he withers away and dies sometime within the next two and a half years.
(HBP10)
The date is deduced from being nine months before Voldemort's birth date. We know Riddle leaves her soon afterward because they were only married for "a few months."
(HBP10)
Merope Gaunt sells Slytherin's locket to [Borgin and Burkes]Pregnant and desperate for money, she has no idea what it's worth and is only given ten [Galleons] for it. The locket is later sold to [Hepzibah Smith].
According to Caractacus Burke, this happened "just before Christmas."
(HBP13)
The older Tom Riddle had previously left Merope when he realized that she was a witch (HBP10), and the child is raised in the [orphanage] (HBP13).
Tom Marvolo Riddle said that he was sixteen years old at the time of Hagrid's expulsion from Hogwarts ([CS17]). Hagrid was expelled in his third year, which was fifty years ago from June of 1993 [[Y13]]. Tom was therefore 16 in 1943 [[Y-37]] - meaning his sixteenth birthday was New Year's Eve, 1942 [[Y-38]], and his date of birth was in 1926 [[Y-54]]. However, according to the official timeline ([CS/DVD]), Hagrid's expulsion was in June of 1942, not 1943, which means that Hagrid's expulsion from Hogwarts was actually fifty-ONE years before June of 1993 [[Y13]]. Riddle was 16, then, in June of 1942 [[Y-38]], and therefore was born in 1925 [[Y-55]]. Either date may be considered correct. However, since the Lexicon follows what is directly given in the books over other sources, the dates in this timeline are derived from a literal interpretation of fifty years.
New Year's Eve is given in HBP13. Depending on exactly when Merope Gaunt arrived at the orphanage, Tom may have been born on New Year's Eve or just after midnight, on New Year's Day. Since the book says New Year's Eve, however, that's what we go with here.
1927 (Y-53) AD = 46 MM = 2 TR = 1
1928 (Y-52) AD = 47 MM = 3 TR = 2 RH = 0
Morfin Gaunt returns from [Azkaban]He returns after a three-year sentence to find both his father and sister, Marvolo and Merope, dead. He lives alone in the Gaunt house for many years, until Tom Riddle returns and frames him for murdering the Riddle family.
(HBP10)
1929 (Y-51) AD = 48 MM = 4 TR = 3 RH = 1
(QA9)
The 1930s
c. 1931 (Y-49)
(GF34)
1931 (Y-49) AD = 50 MM = 6 TR = 5 RH = 3
1932 (Y-48) AD = 51 MM = 7 TR = 6 RH = 4
(FB)
(QA7)
1934 (Y-46) AD = 53 MM = 9 TR = 8 RH = 6
1935 (Y-45) AD = 54 MM = 10 TR = 9 RH = 7
(QA9)
c. 1937 (Y-43)
We know this because [Rowling] has stated on her website that Heads of Houses were members of those Houses when they were students at Hogwarts.
1937 (Y-43) AD = 56 MM = 12 TR = 11 RH = 9
1938 (Y-42) AD = 57 MM = 13 TR = 12 RH = 10
This is based on Riddle's birthday of New Year's Eve, 1926 [[Y-54]].
1939 (Y-41) AD = 58 MM = 14 TR = 13 RH = 11
(CS17)
The 1940s
Events of this decade:
We don't know exactly when [Dumbledore] took the Transfiguration post (except that it was before 1938 [[Y-42]]), but we do know that he taught Transfiguration while Tom Marvolo Riddle was a student (HBP13, HBP20).
[Frank Bryce] returns from fighting in World War Two.He "had a hard war," according to the barkeep at the pub in Little Hangleton. He was wounded and walks with a limp. He takes up as gardener for the Riddles and avoids people for the most part.
[Bryce] came home quite a few years before the end of the war in 1945, undoubtedly because he was wounded.
(GF1)
1940 (Y-40) AD = 59 MM = 15 TR = 14 RH = 12
Meanwhile, Tom Riddle is starting his third year, and Minerva McGonagall her fourth.
The year is based on Hagrid's birthdate of December 6, 1928 [[Y-52]].
c. 1941 (Y-39)
This happened somewhere between Hagrid starting at Hogwarts in the fall of 1940, and his expulsion in the spring of 1943.
(CS)
All we know is that Hagrid's father died during his second year, so it's equally possible that his death was in fall of 1941 or spring of 1942.
(GF24)
1941 (Y-39) AD = 60 MM = 16 TR = 15 RH = 13
Attack on Pearl Harbor
1942 (Y-38) AD = 61 MM = 17 TR = 16 RH = 14
The dates are based on birthdays from 1925-1928 [[Y-55]-[Y-52]].
1943 (Y-37) AD = 62 MM = 18 TR = 17 RH = 15
(BFT)
(CS17)
(CS17)
(CS17)
(CS17)
The next day, Morfin is taken to [Azkaban], where he remains until his death.
"In the summer of his sixteenth year, he left the [orphanage] to which he returned annually and set off to find his Gaunt relatives... Meanwhile, in the village of Little Hangleton, a maid was running along the high street, screaming that there were three bodies lying in the drawing room of the big house: Tom Riddle Senior and his mother and father."
(HBP17)
(HBP23)
"I knew it wouldn't be safe to open the Chamber again while I was still at school. But I wasn't going to waste those long years I'd spent searching for it. I decided to leave behind a diary, preserving my sixteen-year-old self in its pages, so that one day, with luck, I would be able to lead another in my footsteps, and finish Salazar Slytherin's noble work" ([CS17]).
Tom says that he placed his "sixteen-year-old self" into the diary ([CS17]), so he must have done it in the fall after the summer when he killed the Riddles and before he turned 17 at the end of December. His conversation with Slughorn where he learned about Horcruxes must have taken place after school started that September, so the timeframe for the creation of the diary Horcrux is between September and December, 1943 [[Y-37]]. All along, Tom realized that [Dumbledore] was watching him closely (HBP23).
1944 (Y-36) AD = 63 MM = 19 TR = 18 RH = 16
1945 (Y-35) AD = 64 MM = 20 TR = 19 RH = 17
We don't know when this happened exactly, except that it was almost certainly within a few weeks of the end of school. Riddle gets the job at [Borgin and Burkes] "the next thing the staff knew," according to [Dumbledore].
(HBP20)
World War Two ends
c. 1947 (Y-33)

We don't know exactly when this happened, but it is probably within a couple of years of Voldemort's leaving Hogwarts. It's possible this happened later than 1946 or 1947 [[Y-34] or [Y-33]], but unlikely that it happened sooner.
original artwork © [Makani] 2004, used by permission
(HBP20)
(HBP20)
1947 (Y-33) AD = 66 MM = 22 TR = 21 RH = 19
(QA7)
(FB)
1949 (Y-31) AD = 68 MM = 24 TR = 23 RH = 21
The 1950s
Events of this decade:
All this time, Tom Riddle was becoming the evil Dark Lord Voldemort, consorting with the worst of Wizardkind and learning secrets and dark magic that would change him forever from the handsome, talented boy of the 1940s into a twisted, horrible person who would be known as the most evil wizard of his age. One can only imagine that [Dumbledore] kept watch for all those years, waiting and wondering what happened to the boy he knew as Tom Riddle...
1951 (Y-29) AD = 70 MM = 26 TR = 25 RH = 23
This was written in November of 1994 [[Y14]], which would make Rita's birth year 1951 [[Y-29]] on the official time line ([CS/DVD]). Of course, Rita could very well have been lying about her age...
(GF18)
1952 (Y-28) AD = 71 MM = 27 TR = 26 RH = 24
(QA)
1953 (Y-27) AD = 72 MM = 28 TR = 27 RH = 25
(QA7)
1954 (Y-26) AD = 73 MM = 29 TR = 28 RH = 26
He was born 41 years before 1995 [[Y15]], which would be 1954 [[Y-26]].
(OP15)
1955 (Y-25) AD = 74 MM = 30 TR = 29 RH = 27
c. 1956 (Y-24)
(PA18)
(GF27)
1956 (Y-24) AD = 75 MM = 31 TR = 30 RH = 28
"Thirty-nine years this December," said Professor McGonagall brusquely, snapping her bag shut."
She started teaching 39 years before the December of 1995 [[Y15]], so it was 1956 [[Y-24]] on the official timeline ([CS/DVD]).
(OP15)
c. 1957 (Y-23)
Again we don't know exactly when this happened, but since most evidence points to [Dumbledore] becoming headmaster in 1956 [[Y-24]], Voldemort couldn't have come looking for a job much sooner than this.
(HBP20)
1957 (Y-23) AD = 76 MM = 32 TR = 31 RH = 29
So he was born 38 years before 1995 [[Y15]]. This corresponds to 1957 [[Y-23]] on the official timeline. That means he's my age... ([SVA])
(OP14)
(QA7)
1958 (Y-22) AD = 77 MM = 33 TR = 32 RH = 30 M = 0
(QA7)
c. 1959 (Y-21)
For more on the year, see [Marauders' birth year explained].
1959 (Y-21) AD = 78 MM = 34 TR = 33 RH = 31 M = 1
(BFT)
