If a phone screen is the last thing you look at before going to bed, you may be ruining your sleep.
Screens emit bright blue light, which can suppress the production of a sleep-inducing hormone called melatonin.
Without melatonin to make you drowsy, you might be staying up too late. In the morning, you'll feel tired without a full night's rest.
*without jailbreaking them
At a media event on Monday, Apple announced the public release of iOS 9.3, which includes a new feature called "Night Shift" that will reduce your iPhone's blue light when it gets dark.
To get the feature on your iPhone, update to iOS 9.3 by opening Settings app > General > Software Update or connecting your iPhone to your computer and opening iTunes.
(iTunes is usually faster than an over the air update).
Then open Settings > Display & Brightness > Night Shift.
Slide to enable "scheduled" Night Shift, which will automatically turn on a warm display when you go to bed.