You can know the time by vibration without watching your phone. ex. 3: 10 - 3 vibration + sleep + 1 vibration. 7: 37 - 7 vibration + sleep + 3 vibration + sleep + 7 vibration. 11: 30 - 11 vibration+ sleep + 3 vibration. 15: 10 - 3 vibration+ sleep + 1 vibration. 0: 23 - 12 vibration+ sleep + 2 vibration+ sleep + 3 vibration.