I saw your old thread about this question or problem but I am going to add a twist. I have been a single mother twice now. I have 2 boys, one just turned 28 and the other is 14. I cannot tell you how many birthdays I have had ruined because neither of them ever acknowledge them. My oldest son is the worst, and like someone in the previous thread said "there must be underlying issues". I'm guessing that there is but heck if I can get him to talk about anything to resolve them. And the hard part is his birthday is March 15th, mine is March 24th so I go out of my way to give him a nice birthday just 2 weeks prior to mine! Then mine comes along and it's "I'm too busy, I have something else I'm doing, etc". Then I get all hurt and mad and at the same time my youngest son I give hints its going to be my birthday and reminders, guilt trips, nagging and just like his brother, he forgets anyway then gets defensive about it. His birthday is in May and I am darned tempted to "forget" his so he can see how it feels. Then I feel like a shrew and forget about it all by his birthday, and give him a nice birthday as I always do. Then the next year it all goes around again. And it's the same thing on Mothers Day. I'm out of ideas. Do I just finally just give up and stop celebrating?

Why not plan an outing to celebrate BOTH of your birthdays?

Very, very few children in their 20s think of anything except what's going on in their young, complicated struggle. Teens are even worse, and are wishing they were in their 20s and out on their own, and deliberately pull away from parents. I don't blame them. For thousands of years they WERE out on their own by 14, or at least doing the same hard work as their parents instead of having to be half kid, half adult.
I think you are putting too much importance on ceremony. Force yourself to say 'teens and 20s are in a world of their own' and wait patiently, several years. If they are turning out to be respectful, responsible young adults, be glad of that, and don't look for the 'trappings' of love.
And don't go all out on theirs. They don't appreciate it, and might even be embarrassed. All it does is add to your hurt and resentment.

I was born in December. I've been mostly passed over for birthdays my whole life, so I always arranged my own celebration, when I felt like it. I usually invited as many people as I could to a restaurant and didn't mention my b-day - just had a good time! Otherwise they would have felt obligated to bring a card and or gift and probably wouldn't have come.

'Go with the flow.'

Both of my sons have always been good kids, but it wasn't until they hit their 30s that they finally "got it" regarding family birthdays (not just their own). Up until now, I have always prepared a nice dinner or we have gotten special take-out for birthdays and made sure our sons were included. They always showed up! Now they are taking responsibility themselves and contributing to the food and fun.

I think this is a "natural" or normal thing to happen, or I should say, not happen. It's nothing to worry about. People of all ages have different feelings about remembering birthdays, weddings, and about any other event. Some think it's important, some don't.

I hear the pain in your post. Yes it can hurt. I would suggest you sit down and talk to them telling them your feelings. Maybe let them know what you would like for your birthday: a card, phone call, night out, gift, flowers etc. Be very specific. Personally I would suggest not doing the if you don't do this I won't do this for you.
What about inviting them by after supper for cake and coffee. You could also invite friends. If they show great if they don't you still have friends there to help you celebrate.

Thank you so much for your input. I agree with you and I'm sure this is more about me than my children. I also agree that I won't go all out for them as I have. Thanks again!