The verse Domine, labia mea aperies et os meum annuntiabit laudem tuam is sung at the opening of the first canonical hour of the day
Lauds is a canonical hour of the Divine office. In the Roman RiteLiturgy of the Hours it is one of the major hours, usually held after Matins, in the early morning hours (between 3:00:00 and 5:59:59).