Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
고대 사람들은 물시계를 사용하여 시간을 측정했습니다.godae saramdeul-eun mulsigye-reul sayonghayeo sigan-eul cheugjeonghaessseubnida.Ancient people used water clocks to measure time.