The OS system date can be changed by the root account or accounts in the sudo group.
GNOME Automatic Date & Time provides its own timedatectl service rather than use the ntp service via the debian ntp package.
To disable automatic date-time:
timedatectl set-ntp 0
To switch on
timedatectl set-ntp 1
When the timedateclt is disabled, then the date command can be used to set a specific date and or time.
Example: set the date and time
date -s '2024-09-16 21:32:00'
date command will show the current date, confirming that the OS system date was changed.