Question

I created the following code to calculate the duration between two timestamps which can come in two different formats:

public class dummyTime { public static void main(String[] args) {     try {         convertDuration('2008-01-01 01:00 pm - 01:56 pm');         convertDuration('2008-01-01 8:30 pm - 2008-01-02 09:30 am');     } catch (Exception e) {         e.printStackTrace();     } }  private static String convertDuration(String time) throws Exception {     String ts[] = time.split(' - ');     SimpleDateFormat formatNew = new SimpleDateFormat('HH:mm');     Date beg, end;     String duration = null;      beg = getDateTime(ts[0]);     end = getDateTime(ts[1], beg);      duration = formatNew.format(end.getTime() - beg.getTime());     System.out.println(duration + ' /// ' + time + ' /// ' + beg + ' /// '             + end);      return duration; }  private static Date getDateTime(String dateTime) throws ParseException {     DateFormat formatOldDateTime = new SimpleDateFormat(             'yyyy-MM-dd hh:mm aa');     DateFormat formatOldTimeOnly = new SimpleDateFormat('hh:mm aa');     Date date = null;      try {         date = formatOldDateTime.parse(dateTime);     } catch (ParseException e) {         date = formatOldTimeOnly.parse(dateTime);     }      return date; }  private static Date getDateTime(String dateTime, Date orig)         throws ParseException {     Date end = getDateTime(dateTime);      if (end.getYear() == 70) {         end.setYear(orig.getYear());         end.setMonth(orig.getMonth());         end.setDate(orig.getDate());     }      return end; } } 

The output it generates is:

01:56 /// 2008-01-01 01:00 pm - 01:56 pm /// Tue Jan 01 13:00:00 CET 2008 /// Tue Jan 01 13:56:00 CET 2008 14:00 /// 2008-01-01 8:30 pm - 2008-01-02 09:30 am /// Tue Jan 01 20:30:00 CET 2008 /// Wed Jan 02 09:30:00 CET 2008 

My questions are:

1. Why are the results always wrong (always +1h)?
2. What is a better way to identify timestamps without day? == 70 doesn’t look good and the getDay & setDay functions are deprecated too.

Many many thanks, this issue has been driving me crazy for several hours.

Answer 1

1. At my computer this is off by 2 hours, because I’m at GMT+2, and you’re probably at GMT+1. Note that formatNew.format(end.getTime() - beg.getTime()); receives date, i.e. treats your 56 minutes as 1970-01-01-00:56:00 GMT+1. To fix this quickly, call formatNew.setTimeZone( TimeZone.getTimeZone( 'GMT' ) );

2. For the 2nd item, you can check if format-yyyy-MM-dd failed (you catch a parse error), and this is how you know that there’s no year.