I F(34) have been with my boyfriend M(37) for a year and a half, he has two daughters and he spends every other weekend with them. I have no problem with this and our relationship has worked well with this arrangement, however this means that he has missed some important marks for me and our relationship: my first marathon, I had a medical emergency once and I ended up in the ER, our 6 month mark, anniversary, new years, etc. We usually celebrate later. Again, I have no problem with this since I'm very independent and I use these weekends to spend with my friends, family, etc. Also, I work from home and my only responsibility is my dog, so most of the time I adapt my things to do and schedule around what works for him and his daughters.

Now to the issue, our birthdays are 7 days apart this month (April), and this year both fall on a Wednesday. His birthday comes first and the weekend after his is not a daughter's weekend, which means that the weekend after mine is. I decided to celebrate the Friday following my birthday, which I have also been mentioning and telling my friends for about a month now, because I want a specific dress code. Just now he realizes that my celebration is on a day that he can't come and is now mad at me because he says that I should have planned it for a day that he is available and that he feels that I don't want him to be there, which is absolutely not true.

I want to mention that the following weekend is one of my best friend's birthdays and she is having her party that weekend, which means that if I want to celebrate on a day that my boyfriend can be there I have to wait 4 weekends to do so. I love him very much and would love for him to be there, but I feel like it's not the end of the world if he can't go, and if he really wants to, then he'd make arrangements for a day. I've never asked him, nor would I ask him, to change the dates or cancel the weekend with his daughters, but I think this time I don't want to be the person who has to adapt. So AITAH?