find the number of common days between two dates in java code example

Example 1: find difference in days between two dates java

String dateStart = "01/14/2015 08:29:58";
String dateStop = "01/15/2015 11:31:48";

//HH converts hour in 24 hours format (0-23), day calculation
SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");

Date d1 = null;
Date d2 = null;

d1 = format.parse(dateStart);
d2 = format.parse(dateStop);

//in milliseconds
long diff = d2.getTime() - d1.getTime();

long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);

System.out.print(diffDays + " days, ");
System.out.print(diffHours + " hours, ");
System.out.print(diffMinutes + " minutes, ");
System.out.print(diffSeconds + " seconds.");

Example 2: calculate number of years months and days between two dates in java

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
		
Date birth = sdf.parse("2000-01-01");
Date now = new Date(System.currentTimeMillis());
		
Calendar c = Calendar.getInstance();
c.setTimeInMillis(now.getTime() - birth.getTime());
int y = c.get(Calendar.YEAR)-1970;
int m = c.get(Calendar.MONTH);
int d = c.get(Calendar.DAY_OF_MONTH)-1;