Recently noticed time skew across my workstations and servers at home and put together a Stratum-1 NTP server for the local network using the Adafruit Ultimate GPS hat and an RPi 4. I’ll post the write up later. In the meantime, here are the commands I’m using to point all the rest of my RPis at the NTP servers for the local network:

sudo timedatectl set-timezone America/Chicago
sudo timedatectl set-ntp true
sudo bash -c 'echo "NTP=tick.guammie.localtock.guammie.local" >> /etc/systemd/timesyncd.conf'
sudo systemctl restart systemd-timesyncd

You can check and validate with these commands:

timedatectl timesync-status
timedatectl show-timesync
systemctl status systemd-timesyncd