How to set Nextbase dash cam time, it only has GMT

Hey I have a Nextbase 512G which is really annoying me.
1st, I have the GPS set and all working ok, but my time is still saying the time is 1 hour behind.
2nd I have set the time but when it shuts off and I turn it back on, it reverts back to the minus 1 hour.
3rd, It has a section in the menu where you can set the timezone yourself, but all it says is GMT + 1 hr, Minus 1 hour ect.

I have searched everywhere to try find out how to set the correct time, even nextbase user manuals.

Does anyone know which GMT I need to switch it to so it stays at the correct time, and knows the DST as well?

Is it, GMT +1 hour, or GMT +00.00?

Thanks