From Dutch Passions website:
"Autofem seeds can best be grown Indoors under a system of 20-hours light/4-hour darkness over a 10 week period."
I just ran with that because I trust DP and I just dont know any better.
This is also from DP site:
Dutch Passion autoflowering seeds are stable enough to handle permanent daylight, and some growers feel that a 24-hour daylight schedule maximises the harvest potential.
The 24 hour light schedule used for automatics allows them twice the photosynthesis of traditional photoperiod varieties. This, combined with the genetic advances in autoflowering explains the exceptional yields that are possible from the best modern AutoFem varieties