Until Ring makes this feature available natively, we can use Alexa routine. I believe you can use the Alex routine even if you don’t own an echo device by using your phone and the Alexa app.
I just set up two routines, one for arm and another for disarm, at certain time of the day and it is working perfectly.
The routine to disarm was a little tricky but I got it working by using "Disarm Ring. " ". " “.” “.” “. One two three four” as Alexa command. The blank quotes are used to give a little pause (not sure if it is really necessary) and the rest is your Ring voice code.
Hope this helps someone as I struggled for few days trying to figure this out.