Since the auto-hours option does not support multiple answer/no answer times per day, the best way to do this is to create a new OGM for each time-check.
OGMs have an option to do a time-validity-check on the call and decide where to send the call based on a single time condition. What you want to do is to set-up a chain of OGMs in this format:
OGM checks if time is between 18:00 and 08:00, if so send to voice mail, if not send to OGM 2. OGM 2 checks if time is between 13:00 and 14:00, if so send to voice mail, if not send to OGM 3. OGM 3 checks if it is Saturday or Sunday, if so send to voice mail, if not send to OGM with main menu / forward call to agent.