I've given some thought to writing an erotic science fiction novel, and I even came up with what I thought might be an interesting plot premise.
Then I began thinking about some of the unique problems that would need to be dealt with while I was writing such a story. The least immediately apparent one might not turn out to be a problem at all, but I've often had jobs where one of my responsibilities was to anticipate problems and devise ways to deal with them if they happened to come up. So here it is: With publishers and booksellers very sensitive to issues of incest, pedophilia and the like, how do you establish that a character has reached the age of consent?
If you have an SF erotic novel where humans have spread and colonized other planets in other star systems, you can't refer to the old Earth calendar. Other planets would have their own days and years. Even if you had a planet with a 24-hour day, as on Earth, if it completes an orbit of its star once every four Earth years, an '18-year-old' from there hasn't just reached the age of consent, they've shot right past the age of retirement. Spring Break just wouldn't be as much fun there as it is here. Or imagine a world that has no days at all because it's rotation has become tidally locked to its star. Or, alternately, a planet like Uranus in our own system, which has its axis tipped over to such an extent that it seems to be rolling along on its side as it orbits the Sun. What exactly would a 'day' on such a world be?
So, there has to be some galaxy-wide system for determining when boys and girls legally become men and women and can legally start doing the things that erotica readers want to see being done in an erotic novel. I started by doing a little math and came up with one Earth-year being equal to 8760 Earth-hours: 8784 E-hours if you have a leap year, so let's average it out to 8766 E-hours equaling one E-year. An 18-E-year old would then be 157,788 E-hours old. This is an inconvenient figure. In any case, how would you calculate E-hours without some sort of E-watch for each person that you always made sure was properly wound?
As it happens, such a timepiece is already available, based on the absolutely regular decay of certain radioactive isotopes. Okay, it's somewhat more complicated and expensive than the average wristwatch, but the point is that the technology already exists. It can be used without any tweaking at all. Let us call this device an E-clock.
This still leaves that inconvenient figure of 157,788 hours. Now we have to do some serious tweaking. Bump it up to 158,000 hours and you not only have a more convenient number but a 212-hour (8 E-day, 20 E-hour) cushion with which to calm nervous editors and publishers. 160,000 is an even more convenient figure, but now you have that poor character having to wait an 'extra' 92 E-days and 4 E-hours before they can go into the bar in Mos Eisley, that wretched hive of scum and villainy, and legally order something stronger than a Shirley Temple. But now the editors and publishers can breathe even easier, and for the sake of this line of reasoning I'm not going to bring up the matter of fake IDs. Remember, the aim here is to keep editors, publishers and distributors from becoming too nervous. And, if the time of a birth is carefully noted by E-clock time, one does not need a separate watch for each individual.
One possible problem down. More to go.
Either use the SciFi approach with 'standard-year', which should be established if the human culture has established itself on other words.
The other approach (and I'm not sure how that would work with publishers) is to create a culture not fixated with age. 18 hasn't always been the age of maturity and it isn't global today either. In Sweden the sexual maturity age is 15, while the 'legal' maturity age is 18, but Sweden has a whole other bunch of problems when it comes to sexuality and the law. If you don't believe me ask Assage. :-)
Adulthood have for most of human history been linked to such things as getting a home of your own, getting your own food or for some cultures rites of maturity. For a space dwelling civilization why should they still be fixated on age?