: Historical or local administrative reports referencing a "nightly curfew" (zákaz nočního vycházení) starting at 21:00.
: Many devices, such as those using the TimeTune or similar fitness apps, define the "HD" or health-monitoring period for sleep starting from 21:00 (9:00 PM) until the morning (usually 9:00 AM). HD (od 21:00)
: A television program or sports match scheduled for a High Definition (HD) broadcast starting at 21:00 . : Historical or local administrative reports referencing a
: Reports or tests for sleep data are often marked as "invalid" if the user does not wear the device or if the data is recorded outside this specific 21:00 to 09:00 timeframe. Other Potential Contexts : Reports or tests for sleep data are
Depending on where you saw this in a report, it could also refer to:
The phrase most commonly appears in technical manuals for smartwatches and fitness trackers. It typically refers to the Sleep Monitoring (Sleep Test) window . Meaning and Function