That's a simple question with a lot of answers.
You can use variables, holiday tables, time of day tables etc. Start reading Avaya Communication Manager Advanced Administration quick reference guide in the CM5.2 documents.
Simply it can be as follows but can be a lot more complex but a lot more flexible.
01 goto step 11 if time-of-day is fri 17:00 to mon 08:00
02 goto step 11 if time-of-day is all 17:00 to all 08:00
03 collect 1 digits after announcement 1111 for none
04 goto step 7 if digits = 1
05 goto step 9 if digits = 2
06 goto step 3 if digits = none
07 route-to number 1234567890 with cov n if unconditionally
08 stop
09 route-to number 0987654321 with cov n if unconditionally
10 stop
11 disconnect after announcement 9999 (out of hours announcement)
12 stop