If you use an iOS device, you can use the Soro app in conjunction with Apple’s Shortcuts app and create Sonos automations like what you are describing.

https://apps.apple.com/hr/app/soro-for-sonos/id1550457805

Set up two separate ‘alarms’. The first to play Pandora at 8 AM (although I’d be tempted to shift that either way by say 3 minutes, as I would bet the server gots a lot of connection requests right at 8AM) at the desired volume, and then another ‘alarm’ to play nothing (or zero volume) at 5PM. 

Note, each streaming company sets their own limit on how long a stream can play without touching, it wouldn’t surprise me if Pandora was one of those with say a 4 hour limit. In which case you’d set up a second ‘start the stream’ alarm at whatever time it needed to be set at. 

Ah, two more perhaps important notes.
 

Alarms exist on the speakers, not your controller. They’ll work whether you’re there or not.

And unless you set up individual alarms for each day of the week, they should continue to work on Saturday and Sunday, if that matters to you. 

Thank you for such quick responses.  I got it to work!

Judi