How is this int formatted to represent date and time?

Question

I am studying a method I have found in an application called 'getDateTime'. It returns a date and time as one integer. This is then converted by the app and displayed on a label in 24 hour format.

I am not sure how the method is converting the integer it returns - it will not be possible to see this code.

What I can do is override the returned integer and see what date and time is displayed to try and figure out how it is formatted. I would like to be able to convert any date and time to an int of the same format.

Here are some random overrides I did, and what the corresponding printed result was. I have also recorded when the app crashed to give an idea of when the format may be invalid:

• 0 - 00 January 2000 0:00
• 1 - 01 January 2000 0:00
• 2 - 02 January 2000 0:00
• 3 - 03 January 2000 0:00
• 33 - 01 February 2000 0:00
• 65 - 01 March 2000 0:00
• 97 - 01 April 2000 0:00
• 513 - 01 January 2001 0:00
• 545 - 01 February 2001 0:00
• 1025 - 01 January 2002 0:00
• 1057 - 01 February 2002 0:00
• 2002 - Crashed app
• 65537 - 01 January 2000 0:01
• 131073 - 01 January 2000 0:02
• 4194305 - 01 January 2000 1:00
• 8388609 - 01 January 2000 2:00
• 100001 - 01 June 2067 0:01
• 1000001 - 01 March 2033 0:15
• 1029601 - Crashed app
• 1129601 - 01 March 2030 0:17
• 1838382 - 14 Octoboer 2006 0:28
• 35000106551 - 23 February 2031 24:43
• 45000106551 - 23 February 2017 8:55
• 45000106552 - 24 February 2017 8:55

If you need anymore examples to figure out the format, please ask away! I just can't see any correlation, other than the fact that changing the right most digit can be used to change the current day.

Answer 1

It seems that the components of the date (year, month, day, hour, minute) are packed into fields of specific width (similar to the way dates were stored in a FAT directory entry ).

This method will pack the information into the required format:

public static int packTimeFields(int year, int month, int day, int hour, int minute) {
    checkRange("year", year, 2000, 2127);
    checkRange("month", month, 1, 12);
    checkRange("day", day, 1, 31);
    checkRange("hour", hour, 0, 23);
    checkRange("minute", minute, 0, 59);
    return day + (month-1) * 32 + (year-2000) * 512 + minute * 65536 + hour * 65536 * 64;
}

private static void checkRange(String name, int value, int min, int max) {
    if (value < min || value > max)
        throw new IllegalArgumentException(name+" "+value+" is not in valid range "+min+"..."+max);
}

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This code nicely explains the shown examples except

1129601 - 01 March 2030 0:17

I would expect this to be

1129601 - 01 May 2030 0:17