March 1863 — Elmer is born the fourth to John and Helena Macmillan.
1864 — Howard suddenly dies, which makes Helena more protective over her sons, and particularly Elmer.
1866 — His younger and last brother, Lawrence, is born.
1867 — Elmer shows his first sign of magic by suddenly apparating on the roof while Charles was chasing him around in order to torment him. Elmer is happy - his mother less so, as he could have easily fallen to his death.
1868 — Lawrence's weak lungs kill him.
September 1869 — His favourite brother Edward goes to Hogwarts. Elmer is unhappy, because with him gone he has to be all alone with Charles, who is terrible most of the time.
September 1871 — Charles goes to Hogwarts and Elmer is very happy about it - now he has all the house to himself without worrying about his terrible brother.
September 1874 — Elmer finally goes to Hogwarts, where he is sorted into Ravenclaw. He's quiet and bookish, but also nice and friendly, so he has no trouble getting on with his peers.
Hogwarts Years in General — Elmer is naturally bright so he's a good student, though he is also overly fond of poetry and philosophy and such. He hangs out with that folk. One of the electives he picks is ghoul studies.
Elmer also crushes on Miss November Crouch, who he finds to be like a heroine from a gothic novel.
July 1881 — Elmer graduates with excellent grades. He starts working at the Ministry, as an intern for the Department of Magical Law Enforcement. Personally, he'd much rather go for a more scholarly occupation, but he knows that as a third son he can't.
September 1883 — Charles is the first of the Macmillan brothers to get married, to a Miss Noelle Selwyn.
1885 — Elmer convinces his father to loan him some money and with that, combined with his savings from his Ministry job, he purchases Tomes & Scrolls. It's a bookshop/antique shop located in the borders of Diagon and Knockturn Alleys. He quits from his Ministry position and also begins to work on his scholarly research and poetry and such.
1887 — Elmer continues to run his shop. He also reconnects with November Crouch, now Mrs. Malfoy. He doesn't shy away from flirting with her and sending her letters, which are filled with doom and gothic-ness. He finds the fact that she's married terribly romantic. He doesn't even want to sleep with her that much, he just enjoys the whole aesthetic.
1889 — Elmer has sex with a man for the first time. It is Emrys Selwyn, a man known to host and attend the kind of parties Elmer goes to. He enjoys their encounter and isn't opposed to it repeating. It's all very bohemian and poetic and the kind of aesthetic he seeks from life.
1891 — Elmer is nearing thirty. He who seemed to be having a bright Ministry career in front of him is becoming more of an eccentric. He is lucky that his mother loves him so and that his family continues to support him financially. However, there starts to be pressure for him to settle down and leave his Romantic Poet phase behind him.