Getting the difference between 2 dates

Question

Hi,
I am creating a Date object (using today;s day, month and year. hours and minutes come from a config file) and getting the difference between this date and the current date and time.
My code is as follows:
I am passing 07:30 into the method as the parameter aSstart_time.
Calendar newCalendar = Calendar.getInstance(Locale.UK);
    SimpleDateFormat dtformat = new SimpleDateFormat("dd-MM-yy HH:mm");
    int lIYear = newCalendar.get(newCalendar.YEAR);
    int lIMonth = newCalendar.get(newCalendar.MONTH);
    int lIDay = newCalendar.get(newCalendar.DAY_OF_MONTH);
    String lSstartHrs = aSstart_time.substring(0,aSstart_time.indexOf(":"));
    //System.out.println(">>>>>>>>> THE HOURS IS: " + lSstartHrs);
    String lSstartMins = aSstart_time.substring(aSstart_time.indexOf(":")+1,aSstart_time.length());
    //System.out.println(">>>>>>>>> THE MINS IS: " + lSstartMins);
    java.util.Date ldStartTime = new java.util.Date(lIYear,lIMonth,lIDay, Integer.parseInt(lSstartHrs),Integer.parseInt(lSstartMins));
    System.out.println("Year: " + lIYear);
    System.out.println("Month: " + lIMonth);
    System.out.println("Day: " + lIDay);
    System.out.println("Hour: " + Integer.parseInt(lSstartHrs));
    System.out.println("Min: " + Integer.parseInt(lSstartMins));
    System.out.println("The number of milliseconds for current time is: " + newCalendar.getTime().getTime());
    System.out.println("The number of milliseconds for 07:30 is: " + ldStartTime.getTime());
    System.out.println("calendar time: " + dtformat.format(newCalendar.getTime()).toString());
    System.out.println("created time: " + dtformat.format(ldStartTime).toString());
    if(newCalendar.getTime().getTime() < ldStartTime.getTime()){
      System.out.println("The current time is less than the config time (07:30)");
    else{
      System.out.println("The time is greater than 07:30");
    }When I run this program at 10:06am I get the following output:
Year: 2006
Month: 1
Day: 15
Hour: 7
Min: 30
The number of milliseconds for current time is: 1139997962321
The number of milliseconds for 07:30 is: 61098132600000
calendar time: 15-02-06 10:06
created time: 15-02-06 07:30
The current time is less than the config time (07:30)
The Date.gettime() method should measure the number of milliseconds after 01-01-1970 so the number of milliseconds for the current time (10:06am) should be greater than the number of milliseconds for 07:30. A you can see in the above output this is not the case.
Anybody have any idea why this is happening. Am I using the .gettime() method for the correct purpose.
Any ideas or suggestions would be greatly appreciated.
Thanks

Answer 1

It is beacause Calendar use fully defined year as parameter, so Calendar.set(year + 1900, month, date, hrs, min) is (almost) equivalent to new Date(year, month, date, hrs, min)Example:    int year = 85; // old way of specifying a year in a Date
    int month = 3;
    int date = 12;
    int hrs = 12;
    int min = 0;
    Calendar cal = Calendar.getInstance();
    cal.set(year + 1900, month, date, hrs, min);
    Date d = new Date(year, month, date, hrs, min);
    System.out.println(d);
    System.out.println(cal.getTime());You will obtain the same date (except seconds and miliseconds in this case, as they probably won't be zero with Calendar.getInstance(); )