The election of Abraham Lincoln in 1860 was the immediate cause of southern resolutions of secession. He was the nominee of the Republican party with an anti-slavery expansion platform, he refused to acknowledge the right to secession, and he would not yield federal property within Southern states.
The gestation period of a human, from time of conception to birth is approximately 9 months (266 days/38 Weeks). 9.5 months is calculated from the first day of the last menstrual period (280 days/40 Weeks).
On average, the gestation period or length-of-pregnancy of a cow is 285 days long. This is similar to the pregnancy period of a woman, which is closer to around 9 months or ~260 days. However, actual gestation period of a cow can range from 270 days to 295 days, depending primarily on breed[s], age, body condition and nutritional health. Gestation period is also controlled by genetics, but not rate of maturity.