See How To Enable Dark Mode Feature On Samsung Galaxy S20.
#Samsung was one of the first Android companies to add Dark Mode to their smartphones. It's extremely easy to enable UI and set up a schedule if you've recently purchased a Galaxy S20, S20+ or S20 Ultra.
Basically, there is 2 ways by which you van get the darl node enabled on your S20, is either you toggle it on for. The quick panel or from the Settings menu. So both ways are explained below, read on.
The advantage of using the Samsung Galaxy S20's Dark Mode Settings menu is that the app can be configured. You can quickly switch on the Quick Panel app when you don't want to browse through the menu every time you wsny to change the look of the phone's interface
Swipe twice from the top of the screen display to switch to the Quick panel. The Notification Shade is opened with the first swipe. The second one will show an icon grid.
You may have to navigate through parts to find the button, then find the icon that looks like the crescent-shaped moon called "dark mode." Tap the button to turn Dark Mode on or off instantly.
Now it'll be time to turn off Edge Panels, sort the device drawer alphabetically and show a smartphone's percentage of batteries with Dark Mode allowed on your Galaxy S20.
To get the dark mode, head to Settings, Tap on the “Display” option found at the top of the list.
Enable Dark Mode by tapping on the “Dark” button (1). If you don’t want to set up an automatic schedule, tap on the Home button or swipe up from the bottom of the screen if you turned on gesture navigation.
Select the “Dark Mode Settings” option (2) to set up a schedule.
Tap on the toggle next to “Turn On As Scheduled” to enable the schedule feature. The handset will default to “Sunset To Sunrise.” Manually set the Dark Mode schedule by selecting “Custom Schedule” and setting a start and end time.
Source: howtogeek.