Excuses are just gonna make it worse and justify more of how he feels. Admit you messed up and make up for it.

So you realized your mistake.... and then proceeded to lie? Instead of just saying "I just realized I forgot your birthday. I'm so sorry, I can't believe I did that. Can I take you out to make it up to you?" It probably would have been that simple! But nah, you had to go lie and somehow think you have an "FML" because your partner is too smart to believe your B.S... at the end of the day covering your ass was more important to you than just being honest with your partner and making up for your mistake so YDI.

Unless you just started dating you should have just confessed

I hope he had a happy birthday despite his gf forgetting 🙄 Honesty is the best policy.

You fucked up by defaulting to excuses. Could've just come clean with him. Would've made shit so much easier.