I hate the Lunar Calender

I called my parents recently. I felt my mom was not happy. She refused to tell why until I asked it the second time.
"Do you still remember what the date was yesterday?"

Oh my, it's my father's birthday!
I always remembered my parents birthday and called them. But one thing troubles me a little bit is they use Chinese lunar calenders.
It changes every year for solar calendar.

I can do nothing but keep saying sorry. What can I say else? Just because I don't have a lunar calender?
In fact, I've set an alert on my cell phone. But either it didn't work, or I didn't noticed it.

I'm sorry, father. I love you.

Tags: calender family