You're given the power to alter reality for all women starting at 12 midnight on New Year's Eve...

The idea that men are aware that their recognition of women as human beings has been turned off is interesting, as is the idea that they can just flip it back on, but only on an individual basis per woman.

I'm picturing situations where many men are horrified at the thought of allowing a very small number of friends or family members to be treated as animals, but are completely fine using all other women as such - it's a kind of cognitive dissonance that would freak out women even more, as even the guys who might offer to buy them up to protect them would still have no problem eating girl-burgers or bringing home a gallon of milk produced by women.

It would be amazing to see how women all over the world panic as men start to convert farms and slaughterhouses to process women, with women forced on the fly to decide whether or not it's worth it to fight or flee this new world order, or try to get by by offering themselves to a trusted male friend.

How quickly would this reprogramming of men kick in? Instantaneously?

If so, when would you flip that switch?

It's a much more personal cognitive dissonance than that, too. Perhaps there's someone you're protective of, but that doesn't extend to their acquaintances. Enslave your little sister and all her friends, and occasionally just decide to have one of them for dinner. They all know she's closer to immune to being eaten, and individually plead/compete to her to plead/intercede to you to spare them. Whoever sucks up the least that month gets eaten, and you soon have a gaggle of teen girls fighting to make themselves more useful/pleasurable to have around than the others.

Maybe your little sister's primary duty, as your slave, is to make more friends. She knows she's bait, and anyone she befriends will end up being your dinner (and she'll probably be the one cooking them), but if she runs out of girls and the next monthly meal ticks around, it'll be her turning on a spit over coals. And the only reason she's safe enough to go outside to look is the heavy steel and leather collar tightly buckled and padlocked around her throat, shiny ID tag with her name and your contact info jingling from a D-ring. A protection you can revoke with a turn of a key. She's well-motivated to make meals friends.

I was running with OP's premise of the change being instantaneous, though it may take a while for people to realize what has happened and apply it. The instantaneous, immediate effects would probably resemble a wave of domestic abuse as men are suddenly completely unwilling to deal with womens' shit and see no reason to give them the time of day.

The spineless henpecked husband of 20 years just suddenly finds it within himself to backhand his nagging harpy wife, and when she becomes all the more shrill for it she finds herself gagged, hogtied, and left in the bedroom closet until he gets around to remembering that's where he left her.

The lovestruck schoolboy suddenly sees nothing wrong with taking a leash, collar, and padlock to school the next day and claiming his crush. If she resists, that's okay, he brought zipties, and the natural camaraderie of men will likely see him with a couple friends to help out and congratulate him afterwards. She'll probably be stripped naked right on the schoolgrounds to be inspected, and led home wearing nothing but chains. Her father is alarmed when she doesn't come home, but that melts into mild curiosity over her fate in a minute. If he ever finds out what happened to her, his reaction is similar to finding out which team won the game last night, if neither team were ones he cared about.

Women are still allowed to work jobs, but not to keep anything they earn from them. In the modern economy, slavery takes the term "wage slave" and makes it completely literal. A very viable option for comfortable living is to enslave half a dozen or more girls and make their continued existence contingent on pulling a paycheck. A paycheck that they never see, have no control over, and is deposited directly into their owner's account as reimbursement for renting his appliance. Breeding girls for meat is time and effort-intensive, but the long turnaround time makes them good investments that can be cashed out at a premium. Of course, they can be bred as soon as they're capable of delivering.

Cops are stunned to find out but okay with not giving a shit when these reports come in. Female cops that try to respond are relieved of their badges/weapons and locked up as public nuisances, to their great confusion.

Breakthroughs are soon made in every entertainment venue, from stripclubs evolving into brothels where the girls can't say no, to high class establishments where for the right price you can have a purpose-raised 10/10 virgin mid-teen beauty to deflower in every way before cooking her to your specifications. ( Cooking arrangement, the girl's physical traits, restraint options, and her opinion on being used and eaten are all customizable. A girl brainwashed from birth to know that this is her perfect end and to accept a chef's knife with no physical restraints is just as available as a girl who will kick and scream every minute of the way as you prepare her yourself on facility-provided cooking surfaces.)

And of course, there are hunting parties. "Ferals" that attempt to duck the law have no restrained hunting season, and are considered environmental pests with a modest bounty per head. Most simply hunt them as any other animal, but some go out of their way to use rubber slugs to decisively incapacitate their prey before tying it up and carrying it back to camp for any number of uses. Some hunters of large predators will capture women to use them as bait for their real game, as women make a lot more noise than a tethered deer.

Yup. It would be really cute. She'd just melt into a squirming ball of mewling helplessness.

Bonus effect: Superiority of men wouldn't even be debatable. Military, firefighters, cops, etc, all 100% male institutions. Even high-stress jobs like government, CEO, lawyers, etc. Women would be physically incapable of participating. They'd just lock up and cry like a kindergartener being put on stage in front of a crowd for the first time.

Love the idea that the change in all men is instantaneous, even if it takes men months or even a few years to remold society into what they all think it always was (to the point that they might think that the sudden release of women into society and their behavior is the result of some kind of temporary global mass hysteria).

Imagine at noon tomorrow, something flipping over in every guy's head so that they're all suddenly wondering why the women around them are walking upright and fully clothed. Hell, men may not even remember women's names and now only remember them by humiliating pet names that are conjured from thin air - a guy working alone with a coworker suddenly turns around and asks her why she's up on the furniture without her collar. The woman is naturally confused as hell and thinks that maybe it's some sort of prank, at least until her coworker rolls up a magazine, starts beating her with it while yelling "BAD GIRL" and starts ripping off her clothing while kicking her onto her hands and knees.

Now, should reality be altered so men already somehow already have collars and nametags on-hand for the women around them on-hand, or is there a run on pet shops as guys are forced to enslave several billion women all at once?

If we're going the "magical reality/infrastructure shift", you could also have it so that many women already have entries in a global animal welfare database, or at least slaughterhouses and farms are magically converted in that moment to accept women, rather than having to wait months or years for men to convert them themselves…

As little plot magic as possible. The shift takes place entirely in the minds of men, and there's not even physical evidence it has occurred. To all outside observers, it seems that the entirety of the male sex just simultaneously decided like a global psychic gestalt that it was fed up with women, they aren't people anymore, and they never should have been.

Even better when women have mountains of proof available to show that they've always been free and considered to be human, but men are just programmed to ignore that and go on building the infrastructure they now believe was always there in the first place.

A woman shows a guy her ID, and he laughs at the idea she ever had a full name beyond whatever pet name for her is now lodged in his head, to say nothing of the ridiculous idea that such an animal would ever actually have been given a state-issued ID other than animal control tags.

1. No menstrual cycle.
2. Bodily fluids (lethally) poisonous, but only to chads.
3. Sex drive raised to male levels.

The idea that all men suddenly find the idea of any woman having a proper name laughable as an interesting idea.

Maybe this reprogramming comes with a shared knowledge of what "breed" or "class" of animal each woman should be, in keeping with the idea that the reality that supplants men's memories is, to them, a long-established world with its own rules and laws that are completely foreign to all women but suddenly ingrained in men as if they've learned them from birth?

Like, every guy magically now understands what breed a flatchested shorthaired gamine brunette under 5.5 feet would be, and so on.

I love the idea that women would be kept like pets, with larger dog beds, collars and leashes.

The would lay naked together in the dog bed and have whispered conversations:

"I wish I was still a lawyer… Maybe if were good, Dave-"

"-SIR. Omg Mittens, don't let Sir hear you say that. You'll get us in troubles again."

"Can you call me Laura? Like, when its just the two of us? Its like you don't remember what it was like before all this."

"No mittens, and you better call me Blondie. Stop thinking about the before and be happy with what we have. Sir treats us soo good when we're good and make him happy."