Configure proper timezone according to your physical location by using following wizard:
Check time and date settings:
Install ntpdate tool:
Fix problem with ToS (Type of Service) field value in IP packet.
By default ToS is set to 0xc0 value by ntpd daemon.
For now RPi 3 is not able send IP packets via internal wlan0 interface when ToS is set to something different than 0x00.
We can change ToS field value by using iptables following command:
Just put above in below file, before last line (containing "exit 0"):
It will load iptables rule after every reboot of RPi device.
Synchronize time via NTP:
systemctl start ntp
Reboot RPi and verify NTP time synchronization: