The 1970s
Events of this decade:
During the 1970s, [Voldemort] began to gather followers who were eager for a share of his power. The closest followers of [Voldemort] were known as the [Death Eaters]. These years got progressively more dangerous and violent. As [Voldemort]'s influence grew, some witches and wizards were controlled by the Imperius Curse and forced to commit atrocities, including the torture and murder of Muggles. [Voldemort] capitalized on the prejudice and distrust between the giants and the Wizarding World; the giants became [Voldemort]'s followers and killed and tortured many people. The Dark Mark is used by [Death Eaters] to indicate a house where they have committed murder. No one dared to become friendly with strange witches and wizards, not knowing if they were [Voldemort] supporters. Hogwarts became one of the few safe places in the Wizarding World. Bartemius Crouch is head of the Department of Magical Law Enforcement; the Aurors are authorized to use drastic methods not differing greatly from the tactics used by the [Death Eaters] they fight
(QA8)
A rogue [Antipodean Opaleye dragon] kills several kangaroos in [Australia] (FB)
1970 (Y-10) AD = 89 MM = 45 TR = 44 RH = 42 M = 12 BW = 0
This comes from [Dumbledore]'s statement in [PS1] that "we've had precious little to celebrate for eleven years." At that time it is November, 1981. Though we don't know exactly how [Voldemort]'s ascent to power happened, it is probably safe to assume that it somehow took a big leap in 1970.
[Bill Weasley] is bornDetermined from Rowling's statement on her [website] that [Bill] is two years older than [Charlie], who is three years older than [Percy]. We know that [Charlie] was born December 12 two years later - 1972 [[Y-8]]. They will have started school, however, the year they turned 12.
(JKR)
1971 (Y-9) AD = 90 MM = 46 TR = 45 RH = 43 M = 13 BW = 1
(PA18)
This is based on [Lupin]'s birthyear.
(PA18)
[Jo Rowling] meets Ian and Vicki PotterPeter Rowling moved his family to the from Chipping Sodbury to the nearby town of Winterbourne. During the family's residence in Winterbourne, Jo and Di Rowling were friends with neighborhood children, Ian and Vikki Potter.

The [Marauders] start at [Hogwarts][Sirius Black], [Remus Lupin], [Peter Pettigrew], [James Potter], [Lily Evans], and [Severus Snape] start their first year at Hogwarts; all are sorted into Gryffindor except [Snape], who is made a Slytherin
From OP28, we know that [Snape], Black, [Lupin], [Pettigrew], and Potter were all in the same year.
For more on the year, see [Marauders' birth year explained]
original artwork © [Jeannine DellerÈ], used by permission
[Remus Lupin]'s friends discover he is a [werewolf], explaining his monthly disappearances[James Potter], [Sirius Black], and [Peter Pettigrew] then resolve to learn how to become [Animagi] to help [Remus] out, though it will be several years until they master the magic required.
"It took them the best part of three years to work out how to do it.... Finally, in our fifth year, they managed it."
(PA18)
1972 (Y-8) AD = 91 MM = 47 TR = 46 RH = 44 M = 14 BW = 2 CW = 0
(QA7)
[Charlie Weasley] is bornDetermined from [Rowling]'s statement on her [website] that [Bill] is two years older than [Charlie], who is three years older than [Percy]; the actual month and day are also from Jo's site
(JKR)
c. 1973 (Y-7)
1973 (Y-7) AD = 92 MM = 48 TR = 47 RH = 45 M = 15 BW = 3 CW = 1
(FB)
c. 1974 (Y-6)
[Sirius] says in [OP6] that ran away from home when he was about sixteen.
(OP6)
(PA18)
1974 (Y-6) AD = 93 MM = 49 TR = 48 RH = 46 M = 16 BW = 4 CW = 2
c. 1975 (Y-5)
[James Potter] publicly humiliates [Severus Snape] for [Sirius Black]'s amusementThis happens on the afternoon of their [Defence Against the Dark Arts] [O.W.L.], a scene which [Harry] views in a [Pensieve] some twenty-two years later.
(OP28)
[Sirius Black] plays a fateful practical joke on [Severus Snape][Snape] is intensely curious about where [Remus Lupin] goes each month. [Sirius] jokingly suggests that [Snape] follow [Lupin] through the passage beneath the [Whomping Willow]. [James Potter], realizing that [Snape] would encounter a full-blown and very dangerous [werewolf] at the end of the passage, stops [Snape] from going through, thereby waving his life. [Snape], much to his disgust, is indebted to [James] because of this.
(PA18)
We don't know exactly when this happened, but it was around the beginning of the [Marauders]' sixth year.
(PA18)
1975 (Y-5) AD = 94 MM = 50 TR = 49 RH = 47 M = 17 BW = 5 CW = 3
c. 1976 (Y-4)
(PS9)
1976 (Y-4) AD = 95 MM = 51 TR = 50 RH = 48 M = 18 BW = 6 CW = 4 PW = 0
[Percy Weasley] is bornWe know the day from Jo's [website], and can determine the year based on the fact that [Percy] is four years above [Harry] at school.
(JKR)
c. 1977 (Y-3)
The [Marauders] sit their [N.E.W.T.s] and leave [Hogwarts][Sirius Black], [Lily Evans], [Remus Lupin], [Peter Pettigrew], [James Potter], and [Severus Snape] sit their N.E.W.T.s and leave Hogwarts.
Deduced from their birth years.
1977 (Y-3) AD = 96 MM = 52 TR = 51 RH = 49 M = 19 BW = 7 CW = 5 PW = 1
[Cedric Diggory] is born[Cedric] is a fifth-year in PA, which takes place in 1993-1994 [[Y13]-[Y14]]. In GF, then, he's a sixth year student, but he's old enough to participate in the Triwizard Tournament, just like Angelina Johnson. Like her, his birthday must be in the early fall, between the beginning of school and October 31.
(GF16)
[Angelina Johnson] is bornOn October 31, 1994 [[Y14]], [Angelina] says her seventeenth birthday was "last week." This puts her date of birth sometime in late October, 1977 [[Y-3]].
(GF16)
c. 1978 (Y-2)
We don't know exactly when this happened, except that it was sometime between [James] and [Lily] leaving [Hogwarts] (c. 1977 [[Y-3]]) and [Harry]'s birth (July 1980 [[Y0]]). Though, [Molly Weasley] tells us in [HBP5] that couples at this time were getting married very quickly, so it's likely [James and Lily] were married in 1977 or 1978 [[Y-3] or [Y-2]].
For more on their ages, see [Marauders' birth year explained].
1978 (Y-2) AD = 97 MM = 53 TR = 52 RH = 50 M = 20 BW = 8 CW = 6 PW = 2 FGW = 0
(QA9)
[Fred and George Weasley] are bornTheir date of birth is given on Jo's [website], and the year can be deduced from the fact that they are two years ahead of [Harry] in school, among other reasons.
c. 1979 (Y-1)
(PA13)
1979 (Y-1) AD = 98 MM = 54 TR = 53 RH = 51 M = 21 BW = 9 CW = 7 PW = 3 FGW = 1 HG = 0
"DON'T LIE!" bellowed Black. "YOU'D BEEN PASSING INFORMATION TO HIM FOR A YEAR BEFORE LILY AND JAMES DIED! YOU WERE HIS SPY!"
(PA19)
(BFT)
(FB)
[Gwenog Jones] starts her first year at [Hogwarts]She soon becomes a favorite of [Horace Slughorn], the [Potions] Master
(HBP6)
The 1980s
Events of this decade:
c. 1980 (Y0)
This interview had to have taken place sometime after July of 1979 in order for it to apply to [Harry]'s birth in 1980 [[Y0]], and [Dumbledore] describes it as a "cold, wet night" ([OP37]). So it was likely made in the winter or early spring of 1979-1980 [[Y-1]-[Y0]].
We also know that [Trelawney], in early September of 1995 [[Y15]], claimed she had held her post for "nearly sixteen years" ([OP15]), which would imply that she was hired in the middle of a school year. And then, [Dumbledore] says in June of 1996 [[Y16]] that the interview was "sixteen years ago" ([OP37]). So unless [Dumbledore] is wrong, the interview must have been in the first few months of 1980 [[Y0]] - sixteen years before [Dumbledore]'s statement, a slightly exaggerated 'nearly sixteen years' before [Trelawney]'s, and during the time of year most likely to have a "cold, wet night."
1980 (Y0) AD = 99 MM = 55 TR = 54 RH = 52 M = 22 BW = 10 CW = 8 PW = 4 FGW = 2 HG = 1 H&R = 0
It is stated in [Karkaroff]'s scene in the [Pensieve] that he was apprehended just before [Rosier]'s death.
(GF30)
We know from [Sirius Black] that this happened "the year before [Voldemort] fell" ([GF27]).
We know Ernie was born in 1980 because he, [Harry], and [Draco Malfoy] are the only students who are not yet old enough to [Apparate] on the day of the test in [HBP22].
[Draco Malfoy] is born ([JKR], [BFT])
[Dudley Dursley] is bornHow do we know when [Dudley]'s birthday is? Well, we know that [Harry]'s is July 31. A week before his birthday in 1991 [[Y11]], on July 24, [Harry] begins getting letters from [Hogwarts]. At this point, [Harry] is given [Dudley]'s second bedroom, where he discovers Dudley's "month-old" video camera, broken ([PS3]). That camera was given to Dudley for a birthday present ([PS2]) on Dudley's birthday, which must therefore be about a month before July 24.
No, wait, there's more. We know that in the year [Harry] turned 11, [Harry]'s birthday was on a Tuesday ([PS3]) and [Dudley]'s was on a Saturday ([PS2]). Counting back a month from Tuesday, July 24, we find that the nearest Saturday is the 23rd. So regardless of the year in which this is taking place, Dudley's birthday is almost certainly on June 23.

[Harry Potter] is born[Sirius Black] becomes his godfather.
original artwork © [Clio Chiang], used by permission
(PS2)
1981 (Y1) AD = 100 MM = 56 TR = 55 RH = 53 M = 23 BW = 11 CW = 9 PW = 5 FGW = 3 HG = 2 H&R = 1 GW = 0
[Severus Snape] is hired by [Dumbledore] to teach [Potions] at [Hogwarts][Snape] had applied for the post of [Defence Against the Dark Arts], but [Dumbledore] refused.
In October of 1995 [[Y15]], [Snape] told [Umbridge] that he had been teaching at [Hogwarts] for 14 years, but unlike [McGonagall], he did not specify the month ([OP17]). He later says that he took up the post on [Voldemort]'s orders ([HBP2]), so it's almost certain he began teaching at the start of the school year.
The [Fidelius Charm] is cast to hide the [Potters], with [Peter Pettigrew] acting as Secret Keeper[Dumbledore] had offered to be secret keeper, but [James and Lily] had refused, planning to go with [Sirius Black] instead - but switching to [Pettigrew] at the last minute.
Fudge says that the [Fidelius Charm] was cast "barely a week" before [Voldemort] came after the [Potters].
(PA10)
Defeat of [Voldemort]; [James] and [Lily Potter] are killed[Voldemort] attempts to kill [Harry Potter] after murdering his parents, but the spell rebounds onto him.
[Voldemort], nearly dead and without physical form, retreats into the forests of [Albania] where he possess the bodies of various animals to survive for the next decade, waiting. [Hagrid], on [Dumbledore]'s orders, goes to [Godric's Hollow] to rescue baby [Harry] from the ruins of the house.
(PS1)
[Peter Pettigrew] fakes his own death, killing twelve Muggles in the process[Sirius Black] is arrested and at some point in the next few weeks is sent to [Azkaban] without a trial. He is 22 years old.
It's about 90% certain this happened on November 1, but it's also possible it was November 2.
(PA10)
[Hagrid] delivers baby [Harry] to [Dumbledore][Dumbledore] is waiting in [Privet Drive] to leave the baby with the [Dursleys].
but there are [twenty-four hours missing] from the chronology of events of these two days...
(PS1)
[Sirius Black] is framed for the murders of [Peter Pettigrew] and twelve Muggles on November 1, 1981He is sent by [Bartemius Crouch Sr.] to [Azkaban] without a trial.
This almost certainly happened immediately following [Sirius]'s capture on November 1, but we have no way of knowing for sure.
(GF27)
[Bellatrix], [Rodolphus], and [Rabastan] Lestrange, along with [Bartemius Crouch Jr.], are arrestedThey are charged with using the [Cruciatus Curse] on [Frank and Alice Longbottom] in an attempt to discover the whereabouts of [Voldemort]; all of the accused are convicted and sent to [Azkaban]. [Frank and Alice Longbottom] are committed to [St. Mungo's Hospital for Magical Maladies and Injuries], driven permanently insane from the [Cruciatus Curse].
We know that this happened shortly after [Voldemort]'s downfall, as [Dumbledore] says it was "just when everyone thought they were safe." They likely happened sometime between November 1981 [[Y1]] and very early 1982 [[Y2]].
(GF30)
after 1981 (Y1)
(PA18)
