android surprising difference between Date and GregorianCalendar - bug?

Question

I have the following code:

public static final long ONE_DAY_IN_MILLISECONDS = 24*60*60*1000;
(...)
Date newNextTestDate = new Date ( (new Date().getTime()) + newInterval*ONE_DAY_IN_MILLISECONDS);
System.out.println("data: " +newNextTestDate.getTime());

GregorianCalendar tmp2Date = new GregorianCalendar ();
tmp2Date.add(GregorianCalendar.DAY_OF_MONTH, newInterval);
System.out.println(" data2: " +tmp2Date.getTimeInMillis());

//where newInterval is number of days (int)

In Android 4.0.4 and 4.2.2 in 2/3 of cases the displayed values are the same (sometimes minor difference). However in 1/3 of cases there is the difference of.... 3600000 (or something similar like 3600001) which is the equivalent of one hour. Moreover if I have this in a loop, it seems to be fully random, on the same device, without touching any system settings, sometimes that difference exist and sometimes not. Is there any bug in Android implementation of Date?

Answer 1

I don't know what is the reason of problems, but I've found the workaround.

When instead of using new Date() I use (new GregorianCalendar()).getTime this strange "effect" doesn't appear.