This was really interesting. I never knew about all of this. My wife and I celebrate Japanese Girl's and Boy's Day but none of these other customs. Do you think that the Girl's and Boy's Day has just taken over these previous customs? Kinda commercialized it? Either way, very informative post as usual. I have been very busy. I will go back and read all the post that I missed. Cheers.
I didn't know about the history of shichi-go-san either, but I became interested after I started to write this series. After asking a lot of people and doing some research myself to confirm what I was being told, I learned about this celebrations' beginnings in the Edo Period. I suspect that the history of these customs goes back even further and only became formalized during the Edo Period, but I'm not sure.
I would also guess that Girl's and Boy's Day probably started during the Edo Period as well, but I don't know for sure. I'll look into it. Buying a 'kabuto' for boys and a 'hina' doll for girls seems to be pretty traditional. I don't think everyone does it these days, but my father-in-law was pretty adamant about buying these things for my children. I was surprised to see what a big difference there is in price between well-crafted 'kabutos' and 'hina' dolls and their cheaper imitations that many toy stores sell.