Wrong date and time when set automatically

Hi all,

This New Years I suddenly had a lot of problems with my Mac which appear to all have been related to the wrong date and time being set, even though I have set the option to set the date & time automatically.

On 1/1/19 my Mac was setting it's date to 20/9/18 and around 1hr 10m behind the correct time.

On 2/1/19 it's setting it's date to 21/9/18 and around 1hr 10m behind the correct time.

This happens any time I enable the 'Set date and time automatically' option. For the time being I have set the date and time manually.

I have access to 4 other Macs and none of them show this behaviour.

Here is a video to demonstrate: https://youtu.be/MrfMCCpeFFg

Thanks in advance for suggestions.

Dave