I think it all comes down to the individual and there is no standard nor should there be. I knew I liked my Wife from the first day I met her because we just gelled and it was like we had known each other for decades but I didn’t actually ‘love’ her until we had been friends for around six months and it was her that told me she loved me first and she already knew that I was in love with her. We never dated because my Wife hates the term dating and we didn’t call ourselves boyfriend or girlfriend either but everybody knew we were a couple and we were in love. Every relationship is different and love is the strongest emotion that a person can have and I don’t think you can place a time on it because when you fall in love with somebody it comes natural and nobody can decide that for you.