Atkinson is an English-language surname. The name is derived from a patronymic form of the Middle English Atkin.
These are much more conservative than state laws, in general (for instance, everyone should be in a booster seat from about age 4 to at least age 8) but remain less conservative than some of the european standards (for instance, the European Child Safety Alliance recommends that children remain in rear-facing carseats until 3 years of age).
A child should be restrained in a car seat from the moment you take your baby home from the hospital until she grows into adult seat belts, typically around the age of 7 or 8. Every state requires that kids up to 4 years old ride in car seats; most require booster seats for older children.