Well, that's hard to answer since there was no substantial defining moment or turning point. I'd say that it took several months to establish a pattern with the crows and set up a model of interaction. At first, it took awhile to "find" each other—I'd come out of my house, and they'd be busy elsewhere, or they'd be waiting outside for me when I wasn't coming out. It took several months for me to learn their routine, and vice versa.
I should also say that our "friendship" consists of me feeding them and them noticing me. I feed them because I'm interested in them and want to connect, but I can't say the feeling is mutual (although they do love peanuts!).