D-Link DSL-3900 User Manual page 59

Section 4 - Configuration
Schedule: Use the drop-down menu to select the time schedule that the rule will
be enabled on. The schedule may be set to Always, or you can create
your own schedules in the Schedules section. Refer to Schedule on
page 65 for more information.
Click Apply when you are done.
D-Link DSL-3900 User Manual
Port Forwarding (continued)
55