Incorrect date conversion

Question

Today is 5th of May. Following code should output 11th of April and 10th of April. Instead I get 11th of April and 29th of May. Here is the code:

    int daysBack = 24;
    long dayBeginningMilis = getTodaysBeginningMilis() - 86400000 * daysBack;
    Log.i(TAG, "Date: " + new Date(dayBeginningMilis));

    daysBack = 25;
    dayBeginningMilis = getTodaysBeginningMilis() - 86400000 * daysBack;
    Log.i(TAG, "Date: " + new Date(dayBeginningMilis));

private long getTodaysBeginningMilis() {

    // Get milis of todays beginning
    Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
    calendar.set(Calendar.HOUR_OF_DAY, 0);
    calendar.set(Calendar.HOUR, 0);
    calendar.set(Calendar.MINUTE, 0);
    calendar.set(Calendar.SECOND, 0);
    calendar.set(Calendar.MILLISECOND, 0);
    calendar.setTimeZone(TimeZone.getTimeZone("Europe/Kiev"));

    return calendar.getTimeInMillis();

}

Output:

Date: Tue Apr 11 00:00:00 EEST 2017
Date: Mon May 29 17:02:47 EEST 2017

Why is this happening?

score 1 · Answer 1 · answered May 05 '17 at 10:23

I found the culprit. It seems that multiplying integers gets them out of bounds and they are not automatically converted to Long. This change has solved the problem:

long daysBack = 24L;
long dayBeginningMilis = getTodaysBeginningMilis() - 86400000L * daysBack;
Log.i(TAG, "Date: " + new Date(dayBeginningMilis));

daysBack = 25L;
dayBeginningMilis = getTodaysBeginningMilis() - 86400000L * daysBack;
Log.i(TAG, "Date: " + new Date(dayBeginningMilis));

Incorrect date conversion

1 Answers1