7 months.. rock on
6 to 9 months
Your 6- to 9-month-old will probably learn to sit, stand, and perhaps even crawl or consider crawling. The reason we say "consider" is because while infants are generally capable of pulling themselves along with their arms (some even getting up on their hands and knees) by around 9 months of age, the fact is that there are some infants who never crawl.