Invalid Dark mode.

[Lourenzzo!]

Good night! Dark mode does not work at base time, for example: it is now 20:15 and the mode does not change to dark.

Enviado de meu Redmi Note 5 usando o Tapatalk

 

[Igor Eisberg]

Set Location service to "High accuracy" and ensure you have a location lock by GPS (using any app, like Google Maps).

 

[Lourenzzo!]

Thank you! I did not know that location would have to be enabled. Thanks! It worked!

Enviado de meu Redmi Note 5 usando o Tapatalk

 

[Igor Eisberg]

Thank you! I did not know that location would have to be enabled. Thanks! It worked!

Enviado de meu Redmi Note 5 usando o Tapatalk

It works according to the sunrise/sunset times in your region, but doesn't seem to always work correctly.
On Android Q there's an official feature of Dark mode scheduler, which is way more convenient, so hopefully more devices get Android Q in the near future.