I just wanted to know is when and how do you find out when July 23rd was on Cancer?

July 23 is Leo.

Cancer is June 22 - July 22.

The cusp is the turning over from cancer to leo so if you were born at midnight on the cusp you would have traits from both.
You still may have traits from both because I am not sure how much leeway a cusp has.
But you are more leo than cancer.