Try this scenario: Girl 1 is born at 1:30 am in Paris, France on January 2nd. So on every document her birthday is listed as January 2nd.
Exactly one minute later, Girl 2 is born in Boston. In Boston it is 6:31 pm on January 1st. So Girl 2's documents all list her as being born on January 1st, while Girl 1 is listed as born on January 2nd, even though she (1) is older.
Girl 1 and Girl 2 meet up in Los Angeles on January 1st and decide to make a lesbian porn the minute they are both 18. So on January 1st at 3:32 Pm West Coast Time (6:32 PM Boston Time, 1:32 am Paris Time) the cameras start rolling and they get to some hot lesbian action.
Since they are in California, where it is the evening of January 1st, Girl 1 is considered 17, since her documents list her birthday as January 2nd (Though she is exactly 18 years and 2 minutes old). Girl 2 is considered 18, since her documents list her as being born on January 1st.
If the girls make 3 copies of this tape and hand the first copy to Friend A in LA, mail the 2nd copy to Friend B in Boston, and e-mail 3rd copy to Friend C in Paris. Are any of these copies not child porn?
Here about that Lesbian Porn Paradox? Not sure if it was really child porn.