why my js date month is minus 1\ code example

Example 1: minus month javascript date

var d = new Date("January 14, 2012");
console.log(d.toLocaleDateString());
d.setMonth(d.getMonth() - 3);
console.log(d.toLocaleDateString());

Example 2: javascript date 3 months ago

var d = new Date();
d.setMonth(d.getMonth() - 3);