iOS 18 and iPadOS 18 offer a Dark Mode that, in Apple’s words, “delivers a dramatic dark color scheme that looks great across the system and is easier on the eyes in low-light environments.”
To turn on Dark Mode in Settings or Control Center
° Go to Settings, then tap Display & Brightness.
° Select Dark to turn on Dark Mode.
To turn Dark Mode on and off in Control Center:
° Go to Settings, then tap Control Center.
° Tap the Add button next to Dark Mode to add it to Control Center.
To set Dark Mode to turn on automatically:
° Go to Settings, then tap Display & Brightness.
° Select Automatic.
° Tap Options to set a schedule for Dark Mode.
(This how-to is based on my experiences and info on Apple’s support pages — where the images sometimes come from.)