A little one that's bugged me for a while. 

I usually celebrate my birthday with volunteering. 

A coworker I was romantically involved with for a short while wanted to know if I wanted to get together for my birthday a few years so, while we worked together still. We had been broken up for about 8 months. She and I both wanted to be friends, and I genuinely do enjoy her conversation at times.

So thinking she wanted to take me out on my birthday,  I book dinner at fancy place. She told me to go nuts with reservation.

We get together,  dinner wraps up,  lots of alcohol. Bill is big. I'm thinking we'll split it bc I'm not that much of a jerk. She indicates she can't afford it,  she'll leave the tip. I pay a bunch for us both. I do not recall if she left a tip. She drove me home. 

This was years ago. There was no discussion about who pays; I thought it customary to be taken out on birthday at no expense or someplace nice that the person paying could afford - if anyone offers to take you out on your birthday at all. 

I was annoyed and feel I had a right to be,  but clearly I made assumptions. 