Incorrect Daylight and Exercise Time

The daylight exposure and exercise data displayed on the homepage for a single day reflect yesterday's data, not today's. This is mainly to help compare how daytime activities affected last night's sleep.

Today's exercise and daylight exposure can be viewed through widgets or the watch component.

Change the First Day of the Week

The first day of the week follows your system settings by default.
To change it, go to iOS Settings > General > Language & Region > First Day of Week.