To show digital clock always on display we use AMOLED feature of smart phone. This super amoled feature is called ambient display or active display. Always on display (AOD) keep a limited portion of the screen on during sleep mode.

No more frequently charging your phone, over night display and higher brightness of your phone comes to the rescue. In this app you will download a widget and on the widget will be a single slim font show one time text or image time, date and temperature. Even if the app is closed, the screen does not drain your battery.

Super amoled lock screen clock widget does not drain battery because, always on display clock on screen just turns on those pixels LED required to show text, image or graphics while other pixels turned off.

Super Lock Screen: Access the time with just a swipe! Super Lock Screen is a simple, easy to use mobile application for both Android and iOS devices. With a simple swipe on the lock screen, you can see the time in your chosen location, which is formatted according to your time zone. At the same time, you can receive phone calls, see text messages and calendar alerts. No need for an unlock code!
Need a lock screen every day, at a glance, without draining your battery? This alternative to the existing lock screen apps focuses on one thing and one thing only - the time. With a color Android widget (available on many devices) you can check the time on your mobile device at a glance. Just touch the screen or wake it up and it displays the time. The red AM/PM indicator liquid design is intuitive, simple, and elegant and will continue to shine even when the screen is off
Features:
Dark ,Digital & Beautiful Clocks
Uses AMOLED Feature of Android App
No Extra drainage of Battery
Customize Clock Feature
Build Your Own Clock
Modify system settings permission
The app needs permission to modify system settings to change the brightness of the lock screen.

** Note: For Xiaomi devices you will need to access the Security App -> Permissions -> Permissions -> Always On AMOLED -> Display pop-up window permission and Show on Lock screen.