Forgot My Sister's Birthday Again

So today was my big sister Alice's birthday. I had set an alarm last night but somehow ended up snoozing it like a million times, and then when I finally got up it was past noon already. So of course, instead of wishing her happy birthday with all the other family members who remembered on time, there I was in my pajamas while everyone else was getting ready for cake and presents. I told everyone that my phone must have had some weird glitch or something when they asked why I wasn't congratulating Alice earlier. My mom gave me a look but didn’t say anything outright, which made it worse because she knows how forgetful I can be sometimes. Next year I’m definitely going to write the date on my calendar in big red letters and set another reminder just to make sure, this isn’t becoming a yearly tradition or anything. But honestly, I don't think Alice minded too much. She’s super laid back about that kind of stuff anyway. Though now every time I see her smiling with everyone else at the party photos, it makes me feel bad all over again.