As far as I know, quiet hours is a Cortana feature. When I have her enabled, there is a "quiet hours" option in my settings menu. That redirects me to Cortana's quiet hours settings menu. This leads me to believe she must be enabled.
Here's quiet hours in my settings menu
Look at the top of the screen, it says Cortana.
The only way you can turn your ringer off at set times is by using Quiet Hours. You can do this by going to Settings > Quiet Hours, turning on Automatic Rules, and setting the times you want your ringer turned off. Unfortunately, this will work only if your region is set to US.
You should try the built-in Quiet hours feature. It can work only with Cortana as it is a part of Cortana.
When quiet hours is on, any phone calls you receive will go straight to voicemail, and all notifications will be silent (unless you've told Cortana you'd like to hear from the people in your inner circle).
To turn on quiet hours during night ...