Tl;dr on the bottom because this is kind of long

I am 18/F and he is 18/M 

Yesterday was my birthday and my boyfriend and I made plans to spend the whole day together. The first thing we planned to do was go out for lunch and in the morning, he called me and told me that  someone wanted to buy his Apple Watch he was selling on FB marketplace. He asked if it would be ok if we could stop at the Target 5 minutes away from my house before lunch and I said yes. 

When it was almost time to meet up, the guy texted my bf and told him he was on his way (the guy lived in 30 min away from our city) and my boyfriend wanted to go there early so the guy didn’t have to wait. As I was getting ready to leave, my mom asked me if my bf could come in so we can sing happy birthday before I leave since they had other plans later that day so that time was the only time we could do my birthday cake. I figured if we were only gonna sing, he could come in for a minute since the guy wasn’t even at the Target yet. 

When my bf got to my house, I called him and told him to come inside so they could sing happy birthday to me and he got really mad at me and said that we didn’t have time. We ended up arguing for 20 minutes over the phone and he ended up missing my birthday cake because he chose to go meet that guy alone. 

After he sold his Apple Watch, he called me and was upset and told me that he got a bad rating for being late and that it was my fault. I argued the fact that it would’ve only taken 30 seconds to sing happy birthday to me and my mom didn’t expect us to eat the cake right away. He called me unsympathetic and said I needed to admit I was wrong when I feel like I wasn’t. He kept telling me to put myself in his shoes and honestly if I was him I would’ve just came in but he still kept telling me I was wrong. He told me that I didn’t have any right to just “change plans” on him like that and if we made plans then we should stick to them. It made me so upset because I didn’t feel like it would be a huge issue since the guy wasn’t even there her. I ended up crying over the phone and he apologized for sounding mean but he still thinks I’m wrong. So AITA?

After thinking about it, I now feel like I may have been wrong and I didn’t want to tell anyone I knew about this so I’m hoping someone from reddit would be able to share their opinion 

Tl;dr: boyfriend missed my birthday cake because he wouldn’t come in for 30 seconds to sing happy birthday to me and chose to go sell his Apple Watch instead 

