RTC

RB300 and RB350 have a real-time clock with a supercapacitors backup. When the system starts, it takes the time from the RTC if system clock update is failed through NTP.

Useful commands

  • Read hardware clock date and time

    hwclock

  • Copy system time to hardware time

    hwclock -w

  • Copy hardware time to system time

    hwclock -s
  • Set hardware clock date and time manually 
    hwclock --set --date "02/20/2016 11:10:00"

Change system time zone

  • Run: 
    raspi-config
  • Select Localisation options
  • Select Timezone

Network time synchronization

There's a systemd-timesync service running on a default install of Raspberry Pi OS. Systemd-timesyncd is a daemon that has been added for synchronizing the system clock across the network. It implements an SNTP client. Make sure the machine is allowed to query servers over port 123/udp.

To check the service status, use:

timedatectl

The Access/Modify/Change times on this file show when systemd-timesynd last touched it.

Restarting the systemd-timesyncd service force a sync:

systemctl restart systemd-timesyncd

Systemd-timesyncd automatically updates the hardware clock after sync.

Network time synchronization is enabled by default. To disable it use:

timedatectl set-ntp false