Happy Birthday Shinachiku!
Originally, the fandom decided Shinachiku's birthday was April 3rd. Although November 7th was technically the day he exploded in popularity in the NaruSaku fandom, we wanted to stay away from that date because well, who'd want to deal with that?
But a prominent member of the fandom back then wrote a convincing essay on how we should not try to avoid the truth. We should embrace the day Shinachiku "came to life". We should make this day important for that very reason despite HOW it came to be.
And so, everything came together after that. Majority of us agreed that Shinachiku was born November 7th, (2014). Later, when Hanami became a more popular sibling, her birthday was made to be April 3rd, NaruSaku day.
And finally, though I recently learned Arashi became more of a character before Hanami did, his birthday was decided last, July 10th, to match his grandmother who he resembles so much <3