Making the Reader Switch to Night Mode on Its Own

The problem with switching to a dark theme manually is that you do it late. You notice the screen is too bright when it has already been too bright for twenty minutes, because your eyes adapted downward while the display stayed where it was.

A schedule fixes that by removing you from the decision.

How the schedule works

You set a start and an end time. The reader switches to the dark theme at the start and back at the end. The defaults are 19:00 to 07:00, which suits mid-latitude autumn and is wrong half the year — it is a starting point, not a recommendation.

It runs on the clock. Not on sunset, not on the ambient light sensor, and not necessarily on the system dark mode setting.

Why “clock, not light” is a real limitation

In June in northern Europe it is broad daylight at 21:00, and the reader will have gone dark two hours earlier. In a windowless office at 15:00 it is dark and the reader will be bright.

So the schedule is worth setting seasonally, or setting to the hours you actually read rather than to the hours the sun keeps. If you read in bed between 22:00 and midnight, a schedule of 21:30 to 08:00 does the whole job and the daytime edge cases never come up.

An ambient-light trigger would handle those cases better and introduce a worse one: a theme that flips while you are reading, every time a bus goes past a window. Clock-based switching is dull and predictable, and predictable is the correct behaviour for something that changes the page under your eyes.

Set the destination, not just the timing

A schedule that switches to the wrong dark theme is worse than no schedule, because now you are changing it manually anyway.

Pure black on OLED saves power and, for many people, is harder to read at night than dark grey — white on black at low brightness makes edges bloom. Sepia is a third option that suits people who find any dark theme washed out. Which to switch to is covered in choosing a dark mode for night reading; the schedule just decides when.

Pair it with brightness, or it only does half the job

Switching the theme without lowering the brightness leaves the main problem in place. A dark theme at daytime brightness still lights the room.

The reader has its own brightness control, and the combination that works is a dark theme plus a brightness low enough that the screen looks dim when you first switch to it. It will not look dim for long — your eyes adjust within a minute, and the adjustment is the point.

One setting, then stop thinking about it

Set the start half an hour before you normally start reading in the evening. Set the end for whenever you next pick the phone up in daylight. Choose the theme it lands on deliberately.

Then leave it. This is a feature whose entire value is that it stops being something you attend to.