Asking the breeder or consulting the site where you purchased your seeds is going to be the best bet for accurate information. However, as some have mentioned, there are differing opinions.
Technically, autoflowers (or even photos) can take 24 hours of light. Of course, photoperiods won't flower until they get 12 hours of darkness. However as autoflowers will change to flowering stage regardless of light cycle, they can stay in light 24 hours a day. Now, just because they CAN doesn't necessarily mean they SHOULD. During the dark period, plants do different things - they respire differently, photosynthesis changes, different sugars and metabolites move from the leaves to the roots and vice versa, among other things that are important for the overall health of a plant. Basically, a dark period gives the plants a little break kind of like how your body recharges during sleep.
So with all that in mind, it's up to you as a grower to decide or experiment with what works best! One of the coolest things about growing is that you get to f*ck around and find out!