When you construct a String of the format hh:mm:ss for the TimeOfDay property under Lighting with any value greater than 65535, the error “bad lexical cast: source type value could not be interpreted as target” occurs.
This seems to occur when the value 65536 or greater is included anywhere in the TimeOfDay String.
This number is coincidentally also maxUnsignedShort + 1.
The following script causes the error:
game.Lighting.TimeOfDay = (0 ..":".. 0 ..":".. 65536)
I haven’t tested this outside of Studio.
I found a thread on the Roblox forums that dates back to 2009 with this same issue, but couldn’t find it mentioned anywhere here, so it may have just fallen through the cracks.