Is the first day of Leos July 23?
Yes. it is Leo days are actually July 23rd - August 22nd.
Those born with the Sun in the first 10° of Leo (July 23 - Aug 1) comprise the first decan of Leo, whose sub influence is Leo. These are the Leos who have the most typical characteristics of the sign, courage, passionate natures and a love of the spotlight; bombastic, self-centered attitudes and excessive ego.