Select Organization setup.
Call distribution groups or Voice responses (depending on which you want to schedule).
Choose the groups or the voice response you want to edit.
3. Click on the "Calendar"
4. Click on "New schedule event".
Here you'll be able too set when the event will occur. You can set if it should be a returning event (like opening times) or if it's just for a holiday or such.
The example down below shows us it's going to be closed from 08:00 the 24th of December to 08:00 the 27th of December.
You can also set what prompt you want to be played when people calls. If you would like to record a new prompt, you can press the cog to start recording.