zil

This is the only reason I need

I was thinking others could help build the list.  Some are obvious (there are actually 24 hours in a day, not 12; time math is easier; you don't have to ask whether "at eight" is AM or PM; etc.).  But some are fun - like The Great Salad of 1810.

I really appreciate the title suggesting there are multiple reasons for using military time, but only offering 1 reason... yet that 1 reason is better than any comprehensive list one could possibly come up with

It was a long day.

You can describe your dinner as: "The Great Salad of 1810".

Dinner, not supper.  

This is one of my big philosophical disagreements with progressivism:  it takes an almost narcissistic position, suggesting that our current society is the inevitable culmination of all history, but for—perhaps—a smattering of final “tweaks” that will make things truly perfect; and it assumes that the things we like about the status quo are essentially self-perpetuating.  
The reason we don’t crucify religious or social heretics isn’t that we don’t still want to silence heretics, or that we are now immune from waves of social hysteria that lead us to want to inflict terrible suffering on others.  The reason is that right now we live in a society that has worked very hard to devise and maintain systems of government that simply didn’t give people the power to do all that was in their hearts.    Put a weak government like Weimar Germany in power and give it a decade or two, and it may as well be 1500 again.  
The reason we don’t have slavery is that we don’t need it.  If you’re a conservative like me, you’d point out that the masses can use government to appropriate for themselves the value of the saving and investment and labor and prudence of others.  If you’re a leftist, you’d point out that social systems like capitalism allow the indolent wealthy to take what they want from virtuous workers under color of law.  Either way, though—take those redistributionist institutions away, and you’ll be right back to a primitive state where the strong and/or amoral will be more than happy to take what they want from the weak and/or moral, by any means and with whatever force necessary.  
The reason we don’t murder each other for religion is that a few centuries ago we were blessed with genius ancestors who suggested that we shouldn’t do that; and once they’d had their way for a generation or two a few more geniuses figured out that letting heretics live might be to our mutual economic advantage; and our economic experience then tended to bear that out and make us not care so much about dogma.  When the economy tanks and/or the social order seems otherwise to be in decay, heretics and social outcasts don’t do so well—see, e.g., the recent emboldening of white supremacists in America’s “rust belt” and the rise of what you’d call “far right” groups across Europe.
The reason we pay more attention to domestic violence isn’t that we at one point thought it was OK; we simply didn’t have the social institutions to be very interventionist about it. Part of that was social stability, part was technology . . . And part of that was the fact that until very recently, there was simply no secular government that could be trusted to wield that kind of power over family life in a benevolent manner (some of us would say there still isn’t.  Didn’t your own NHS just put a couple of kids under house arrest until they died, over the objections of their parents, because NHS didn’t want to risk the humiliation of the American health care system curing children that NHS doctors had said were terminal?  Didn’t Venezuela, formerly one of the most stable democracies and strongest economies in Latin America, just get caught rationing health care for political gain?)
If we have progressed so far, why is it still legal across the western world to kill children by literally tearing them apart, limb from limb, until they die—and just so that their “mothers” don’t have to get fat for a couple of months, and so their “fathers” don’t have to pay money for their care and maintenance?  You think we’ve moved behind genocide and holocaust?  We’re in the middle of one right now.  We’ve just trained ourselves not to look.
If Nazi Germany has taught us anything, it’s that no matter how much we pat ourselves on the back for our degree of “civilization”, the sixth century BC century is never more than a decade or two away.  The only difference is that this time we have surgical scalpels, and cyanide gas, and gunpowder, and nukes.

Dinner is at XII:XLV, but you keep missing it because you don't speak Roman.

You can describe your dinner as: "The Great Salad of 1810".

You can describe your dinner as: "The Great Salad of 1810".

You can describe your dinner as: "The Great Salad of 1810".

https://www.lds.org/study/manual/handbook-2-administering-the-church/selected-church-policies-and-guidelines/selected-church-policies?lang=eng#title_number71
Especially:
Handbook 2 answers a multitude of questions.

Resulting, of course, in “The War of 1812” (spoiler:  the wife won).

You can describe your dinner as: "The Great Salad of 1810".

hmm, seems to re-made from another knife.
 

I think it’s been pretty easy for apologists to categorize past policies as, at least, being appropriate for the time and place in which they existed.
This one is harder, because as @Midwest LDS says—what has changed in the last three years, really?  
(Other than, the mass apostasy of featherweight Mormons who couldn’t reconcile themselves to the 2015 policy.  Hmm, maybe that’s it.  Maybe it was supposed to be another “Zion’s Camp”/wheat-versus-tares sort of moment . . .)

Pffff.  You say that now.  Wait until your home is surrounded by Orcs.

Anduril, from Lord of the Rings.

Pffff.  You say that now.  Wait until your home is surrounded by Orcs.

And now, for your viewing pleasure, one of the finest-looking knives1 ever made:

It's enough to make a girl swoon.
1Not available in the UK.

With an eth? "Nthstril"? Looks like "Nostril". "Narsil", perhaps?

Well, to be correct, Andúril was the name given it by Aragorn after the thing was reforged on the heels of the Council of Elrond.  It's old name was Nðstril.
 

Anduril, from Lord of the Rings.

And now, for your viewing pleasure, one of the finest-looking knives1 ever made:

It's enough to make a girl swoon.
1Not available in the UK.

And now, for your viewing pleasure, one of the finest-looking knives1 ever made:

It's enough to make a girl swoon.
1Not available in the UK.