Its FMLA and each state is different. Where I'm at its 8 weeks if you take time off before the baby is born, and 12 weeks if youtake off after the baby is born. I believe some states you must take vacation time if you have it left.
12 weeks...I was able to take 1 week as paternity after birth of child. Followed by an additional 11 weeks under FMLA prior to the childs first birthday. All vacation/option days were paid out for FMLA with the the option to save 1 week as vacation. Your area may differ.