Why does Screen Time show usage when my iPhone is turned off?

This is an interesting issue with Screen Time showing activity when your phone is supposedly off. There are a few possible explanations:

1. "Off" vs. "Sleep" - Your phone might be in sleep mode rather than completely powered off. When in sleep, background processes can still run and register as device usage in Screen Time.
2. Time zone or synchronization issues - If you've recently changed time zones or if there's a sync delay between your devices, Screen Time might display data incorrectly.
3. Shared Apple ID - If you use the same Apple ID on multiple devices, Screen Time might be showing combined usage from another device like an iPad or Mac.
4. System services - Some system services might register as "Phone" usage in Screen Time even when you're not actively using the device.
5. Screen Time glitch - It could simply be a bug in the Screen Time feature.

To troubleshoot:

• Make sure you're fully powering off your phone (press and hold the power button until "slide to power off" appears, then slide)
• Check if you're using the same Apple ID on other devices
• Try resetting your Screen Time statistics (Settings > Screen Time > scroll down to "Clear Usage Data")
• Make sure your date, time, and time zone settings are correct
• Consider updating to the latest iOS version if you haven't already

If this continues after trying these steps, it may be worth contacting Apple Support directly as they can look more specifically at your account configuration.