Thanks to the power of *dun, dun, dun* THE CLOUD…we are able to work from any place, at any time. While that is great for flexibility, being “always on” can become exhausting. Luckily, Microsoft has introduced Quiet Hours in the Microsoft Teams mobile app so we can make sure our work/life balance stays in check.
By using Quiet Hours, we can not only mute alerts at specific times of the day, but also select Quiet Days where no notifications are sent.
It's Partly Cloudy 
How to change on desktop?
Hi Mac, as of now I this is not an option in the desktop version. You could suggest the feature on uservoice though https://aka.ms/teamsfeedback