Always use a moisturizer for daytime and one for night. A moisturizer for day should be one with an SPF and feel lightweight. A night moisturizer should be a heavier creme (or lotion for oily skin) to replenish loss of hydration and skin cells, rejuvenate, and help keep elasticity in your skin. Normally a night moisturizer will have some type of ingredient (AHA, essential ingredients, firming properties, etc.) to help keep skin in youthful condition.