i doubt if b-acd has a time check capability. you could do this using a CUE module which is a cheaper investment.
Not sure instead of forwarding calls, Nighbell in CME will solve your problem. This helps to assign a night bell and say the receptionist is not available during the night time, when a call comes in, a ring is heard on (say) the security guard's station who can then pick up the call using call pickup.
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_administration_guide_chapter09186a00801f1135.html#wp2177466
HTh
Sankar
PS: please remember to rate posts!
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus