IIRC, I read somewhere that both Tsunade and Sakura are both older than Orochimaru and Jiraiya and Sasuke and Naruto, respectively, so the studio/mangaka may want to keep up the trend. Could be wrong but if Sarada's birthday is the last day of March, then that gives Boruto only a 3-month window from the start of the year to be older than her ... When you register your boat in california you will get a certificate of number and what else