Plot hole: The parents meet and get married on the QE II and then we jump to the girls getting to camp 11 years and nine months later. We learn their 12th birthdays are on October 11, so at the time of the camp (which must be around July/August) they are 11 years and around 9 months old. They should only be 11, given it takes 9 months to grow a baby, but instead they're nearly 12.
Suggested correction: Elizabeth James got pregnant sometime within the 11 years. Their parents sent them to camp in July because in October they both turn 12. So they are 11 years 9 months old.
The mistake is valid, but perhaps not specific enough about why. The opening scene takes place Jan 8, 1986 (as seen on the marriage licence). Then it says 11 years and 9 months later, which would mean in the next scene it's October 1997 (when it's July 1998). It's 11 years and 9 months after the twins' birth and/or the parents' divorce. But we're not actually shown that part.
