Hd (od 21:00) Direct

: 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).

Depending on where you saw this in a report, it could also refer to: HD (od 21:00)

: Historical or local administrative reports referencing a "nightly curfew" (zákaz nočního vycházení) starting at 21:00. : Many devices, such as those using the