计算两个日期相隔的天数（jodd）

public static void main(String[] args) throws ParseException {
        System.out.println(TimeUtil.dayOfYear(1992, 12, 31));
        System.out.println(TimeUtil.dayOfYear(2016, 3, 14));

        JDateTime time = new JDateTime(new Date());
        JDateTime time2 = new JDateTime(new SimpleDateFormat("yyyyMMdd").parse("20160310"));

        System.out.println(time2.daysBetween(time));
}

daysBetween源码分析

/**
     * Calculates the number of days between two dates. Returned value is always positive.
     */
public int daysBetween(JulianDateStamp otherDate) {
        int difference = daysSpan(otherDate);
        return difference >= 0 ? difference : -difference;
}

/**
     * Returns span between two days. Returned value may be positive (when this date
     * is after the provided one) or negative (when comparing to future date).
     */
public int daysSpan(JulianDateStamp otherDate) {
        int now = getJulianDayNumber();
        int then = otherDate.getJulianDayNumber();
        return now - then;
}

/**
     * Returns JDN. Note that JDN is not equal to {@link #integer}. It is calculated by
     * rounding to the nearest integer.
     */
public int getJulianDayNumber() {
        if (fraction >= 0.5) {
            return integer + 1;
        }
        return integer;
}