To not accommodate DH holiday plans

I agree with everyone else. But, also, how often do you get to go away and leave him with the kids? I suspect I know the answer to this, but trying not to assume.

My worry, especially if you think he might be trying to sabotage your job, is that he will go and simply not come back on Sunday leaving you literally holding the baby on Monday morning. I think you need to make it crystal clear to him that if he pulls a stunt like that then you will be leaving the house extra early on random days in future to leave him in the lurch so he knows what it feels like.

Point to the family calendar and tell him you cannot re schedule your work commitments as he has failed to write it down.

Then ask him to help arrange childcare for that day.

He’s a man child, whilst he’s gone back his bags

He's so in the wrong. But I think it will be hard for you not to swoop in and fix this, especially if he persists with being in a mood and making everything shit for everyone. I know I would find I hard and probably cave. I hope you don't though!

And Mrs.NotWashingTowelsDaily (for his benefit) has to make it clear she’s not being deliberately awkward to ruin his holiday plans because she’s a curmudgeon!

I was going to say YABU until the bit about your DC having special needs and you having no way of resolving that.

Does HE have any suggestions to resolve it?

When do you get a holiday and fun without also having to do all the arranging? He gets to swan off when he wants, with one simple caveat; discuss the dates first.

I can’t believe he thinks you’re the problem. Do you love him?

Tell him you're having a weekend away yourself next when he gets back

Are there any positives to your marriage? It reads like he does what he wants, when he wants, while you work / organise the household/ do the majority of the childcare. It's not a partnership if he just see you as the housekeeper/ nanny.

Does he not acknowledge that he made it difficult for himself by getting his dates wrong and not organising himself properly? Wild that he's blaming you for his cock-up.

Great idea, 'I promise not to be a selfish arse and to remember I'm a grown up and a parent', signed Mr @NotWashingTowelsDaily

I think it might be an idea to put the next agreement in writing and have both signatures on it.

Not much of a family unit is it? It's just him doing what he wants when he wants. You have been too accommodating for too long. You have work meetings, he will have to fix this.
Also, stop excusing him, lots of us have jobs and lives that can be stressful, we don't all bog off on holiday leaving others to pick up the pieces. He just sounds really rubbish.

That makes it even more important that you prioritize work over him having an extra day.

Don't let him fuck with your job no matter what.

You might want to start lining up some ducks if you think this is possibly the case. Get copies of everything, research home health care, respite care, and look into lawyers. Just to have in case.

You are clearly the default parent and he previously paid lip service to rearranging but hasn’t taken on what has been agreed. Stand firm. You had an agreement and as long as the Monday is your normal working day, then this is his problem to solve. The more you give in and juggle the more he will exploit you. I imagine he earns masses more than you so feels entitled. Book yourself a long weekend away - it’s really the only way he will learn.

Good on you for pushing back and not solving the problem for him.

What was his actual response when you reminded him of the previous discussion and how this behaviour of his has already caused issues which is why he agreed to stop doing it. Is he accepting any blame here or responsibility for getting the dates wrong and messing you about?

The system you thought had just been put in place - each check with the other before booking and as soon as the dates are firm - is pretty much essential (IME, anyway) and probably should have been in place as soon as the two of you had children. That obviously includes going through the same process with any changes of dates, not doing that would defeat the whole purpose of the process. People make mistakes and if that's what had happened I would try to accommodate him (and vice versa, if I made the mistake) but if it's not possible then the options are for him to line up outside childcare or for him to adjust his (not necessarily his friends') trip. His acting like YOU are being unreasonable because you can't accommodate the last-minute change doesn't make sense. If he's acting as if he needn't have told you about the change and of course it was OK, that seems either disingenuous and manipulative or incompetent.

It’s been agreed he goes away but he’s added the extra day on skewing the arrangement.

Context is everything - if an otherwise caring and respectful partner made an error on a flight booking etc I would be happy to help. But given the history here and his consistent lack of respect for you or your time, you are 100% in the right.

Do you think he'll just go anyway, regardless of what you say?