The time of Great Ruins hadn't matched that of Supreme Emperor Heaven, and because its algebra was too bad, the suns' cycles didn't even consist of twenty-four hours. Because of that, the day and night times of Supreme Emperor Heaven weren't accurate.
After Qin Mu had destroyed one of the suns, Eternal Peace Imperial Preceptor forged a sun which used the twenty-four-hour cycle of Eternal Peace Empire.
However, Imperial Preceptor had an obsessive-compulsive disorder, so he tried to perfect everything. The moment the sun lit up, it matched the sun of Eternal Peace. This meant that the moment the darkness descended on Great Ruins was also matched without a second's difference.
It was night time in Great Ruins at that moment.
There were only two ways to travel in the darkness of Great Ruins. Otherwise, the person would die miserably from either a curse or being eaten by monsters in the darkness.
