Will Libra forgive?

I'm an Aries and have been seeing a Libra in another city, casually. I recently told him I want it to be more and I'm pretty sure he has been open to that for awhile. So I'm planning on being in his city before leaving the country for a month, and told him I would be at his place, but not at a certain time. He misunderstood and waited for me. Of course, it took much longer than expected preparing for a month away, and I neglected to call.
He is so angry, saying how this is why we never got together before, and how downright unfriendly it was for me not to call. There doesn't seem to be anything I can say or do.
I know I should have called. It was a terrible mistake. It just seems his response is worse than I ever thought.
How do you apologize to a Libra who knows he is in the right and won't budge even a little.
Am I getting what I deserve? I know I can be irresponsible with feelings sometime, and I'm truly trying to work on it.
Any advice?

If it is of any help, I'm a 33 year old male, and he's 50.

You show him your vulnerable side, and from the deepest part of your heart, you say that you are sorry.
I hate not being called back. It makes me worry about any number of things, from not having any interest anymore, to something bad happening to them. Our analytical minds will weigh in the reasons behind things and it can get very taxing. This is probably why he is mad at you, because you put him through all of this.

libras usually forgive if you continue to try. it just takes some effort. they want to know you mean it.