1.計算兩個日期之間相差的天數
Java, Calculate the number of days between two dates
// http://en.wikipedia.org/wiki/Julian_day
public static int julianDay(int year, int month, int day) {
int a = (14 - month) / 12;
int y = year + 4800 - a;
int m = month + 12 * a - 3;
int jdn = day + (153 * m + 2)/5 + 365*y + y/4 - y/100 + y/400 - 32045;
return jdn;
}
public static int diff(int y1, int m1, int d1, int y2, int m2, int d2) {
return julianDay(y1, m1, d1) - julianDay(y2, m2, d2);
}
2.獲取當前日期
How to get the current date/time in java
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = new Date();
System.out.println(dateFormat.format(date)); //2014/08/06 15:59:48
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Calendar cal = Calendar.getInstance();
System.out.println(dateFormat.format(cal.getTime())); //2014/08/06 16:00:22
3.獲取當前年/月/日等信息
How to get year, month, day, hours, minutes, seconds and milliseconds of the current moment in Java?
Calendar now = Calendar.getInstance();
int year = now.get(Calendar.YEAR);
int month = now.get(Calendar.MONTH) + 1; // Note: zero based!
int day = now.get(Calendar.DAY_OF_MONTH);
int hour = now.get(Calendar.HOUR_OF_DAY);
int minute = now.get(Calendar.MINUTE);
int second = now.get(Calendar.SECOND);
int millis = now.get(Calendar.MILLISECOND);
System.out.printf("%d-%02d-%02d %02d:%02d:%02d.%03d", year, month, day, hour, minute, second, millis);
