diffInMonths = function diffInMonths(a, b) {

	var wholeMonthDiff = (b.getFullYear() - a.getFullYear()) * 12 + (b.getMonth() - a.getMonth());
	var anchor = addMonths(clone$1(a), wholeMonthDiff);
	var anchor2 = void 0;
	var adjust = void 0;

	if (b - anchor < 0) {
		anchor2 = addMonths(clone$1(a), wholeMonthDiff - 1);
		adjust = (b - anchor) / (anchor - anchor2);
	} else {
		anchor2 = addMonths(clone$1(a), wholeMonthDiff + 1);
		adjust = (b - anchor) / (anchor2 - anchor);
	}

	return -(wholeMonthDiff + adjust);
}
Difference in months between date `a` and date `b`
@param a
@param b
@returns {number}