Question

I have a datepicker, and I pick up two dates, like 2012-04-08 and 2012-05-11. Because I have a database and need store dates as strings I convert them to 20120408 and 20120511 (strings so far). My code contains the next steps. I call my function with these strings:

public void durva(String datefrom, String dateto) throws ParseException {

    datefrom = GlobalVars.getDateStringFrom();
    dateto = GlobalVars.getDateStringTo();

    Log.i("DateFrom", datefrom);
    Log.i("Dateto", dateto);

    SimpleDateFormat formatter2 = new SimpleDateFormat("yyyyMMdd"); //-de most yyMMdd
    formatter2.setLenient(false);

    Date dates1;
    Date dates2;
    long mili1;
    long mili2;

    long diff;

    String dates="";
        String convertedDates = "";

    dates1 = formatter2.parse(datefrom);
           mili1 = dates1.getTime(); 
           Log.i("date1",  String.valueOf(mili1));
   dates2 = formatter2.parse(dateto);
           mili2 = dates2.getTime(); 
           Log.i("date2",  String.valueOf(mili2));

   diff = 1+((mili2-mili1)/86400000);

   Log.i("diff",  String.valueOf(diff));

   long [] millis = new long[(int) diff];


   for (int i=0;i<diff;i++)
    {
        millis[i] = mili1+(86400000*i);
         Log.i("millii",  String.valueOf(millis[i]));
    dates = dates + String.valueOf(millis[i]) + " ";   


    SimpleDateFormat formatterX = new SimpleDateFormat("yyyyMMdd"); 
    String dateString = formatterX.format(new Date(millis[i]));

          convertedDates = convertedDates + dateString + " ";
    }
      Log.i("DATES",  convertedDates);
      } 

I use the a created GlobalVars when I pick a date and covert them to this string format I mentioned above. Then I convert them to millisecs. Then I convert them back to my format but it is not important, since the millisecs are already messed up. With

for (int i=0;i<diff;i++)
        {
            millis[i] = mili1+(86400000*i);
             Log.i("millii",  String.valueOf(millis[i]));

I always increase the millisecs, but what happens after the 25th value? It travels back in time and continues from another value! In this example I get: 20120408 20120409 .. 20120502 20120314..20120322 . I add 86400000 (millisecs per day) for jumping a whole day.
What’s happening here?
Thank you in advance!

Answer 1

You should use 86400000L, or declare i as long:

millis[i] = mili1+(86400000L*i);

Otherwise both i and 86400000 are 32 bit integers, so the result is calculated as a 32-bit integer. Unfortunately 86400000*25 is too big to fit in 32 bits, so it wraps around.

86400000*25 is -2134967296.

Another thing you should be careful about is that not all days have 24 hours thanks to DST.