I work at an assisted living facility. We work 24 hour shifts. I am paid regular rate for 12 hours, overtime for 8 hours and not paid at all for the remaining 4 hours because the owner calls it "sleep time". I am still there and unable to leave and must still tend to the residents needs whenever they need me. Is this legal?

Thank you!
Cherie

The first link here is if your period of work is less than 24 hours. The second is for work periods of 24 hours or more.
http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_785/29CFR785.21.htm
http://www.dol.gov/dol/allcfr/ESA/Title_29/Part_785/29CFR785.22.htm