How do you calculate what age interval of the ASQ-3 should be used? The age calculator on the website sometimes gives an age that is slightly different than if I calculate by hand using the instructions in the User's Guide. Why does this occur? When calculating a child's age to choose the correct age interval, does the date administered count as a complete day in the calculation? When calculating a child's age, what is your month equivalent in weeks? If a child is 44 weeks old, is he 11 months old?