Traditionally, the Gayatri mantra is recited or chanted 108 times on three occasions daily – at sunrise, at midday and at dusk, when the sun is setting.
It can be repeated in totals of 108, 1,008, 10,008, etc.
When we repeat the Gayatri mantra three times over the day, we are basically affirming the concept of the trinity of life – birth, growth, death.