[SOLVED] Seconds since 12:00 am December 31, 1989 Java

Seconds since 12:00 am December 31, 1989 Java

I have to get the count of seconds since 12:00 am December 31, 1989, to now. The second parser comes from Garmin Fleet Management. Here is my code:

public int getDate(){
    Date d1 = new Date(1989, 12, 31, 12, 0, 0);
    Date today = new Date();
    long diff = today.getTime() - d1.getTime();
    return (int)(diff/1000);
}

Seconds from getDate() in Garmin parser shows as 08:35 pm July 28, 2021, instead of now.

Here is explained (by documentation) date time that I need

It is an unsigned 32-bit integer and its value is the number of seconds since 12:00 am December 31, 1989, UTC.

Where I made a mistake?

Solution

You should return long and wrap your difference to Math.abs() for the positive result expressing the difference.

public static long getDate() {
    Date d1 = new Date(1989, 12, 31, 12, 0, 0);
    Date today = new Date();
    long diff = Math.abs(today.getTime() - d1.getTime());
    return (diff/1000);
}

There is no unsigned in Java.

Morover this constructor for Date is obsolete, so using of Calendar is the better way:

public static long getDate() {
    Calendar d1 = new GregorianCalendar(1989, 11, 31, 0, 0, 0);
    Date today = new Date();
    long diff = Math.abs(today.getTime() - d1.getTime().getTime());
    return (diff/1000);
}