convert time from int in c

Question

If I have an integer in c that represents the date how do I print out the actuall mm/dd/year?

64-bit value representing the number of 100-nanosecond intervals since January 1, 1601 (UTC)

1183042181

what if I am on a 32 bit system, and have to read the integer in from a file?

C not C++

Answer 1

Put the time into a struct tm and call strftime().

It's all declared in <time.h>.

Answer 2

Read the MSDN section:

Remarks

To convert a FILETIME structure into a time that is easy to display to a user, use the FileTimeToSystemTime function.

Answer 3

C's library contains the strftime function, which will format a struct tm using a specified format string. From there, of course, you can print it. So:

• Convert your FILETIME to seconds since 1601 by dividing by 10,000,000.
• Convert to a standard UNIX timestamp by subtracting the number of seconds between 1601-01-01 and 1970-01-01.
• Use localtime() to convert that to a struct tm.
• Use strftime() to get a formatted string.
• Print it.
• Write a function to do all of this so you don't have to do it again.

Answer 4

You can use this routine to convert your 64 bit value to time_t structure

time_t FileTimeToUnixTime(FILETIME& ft)
{
    ULARGE_INTEGER li;
    assert(sizeof(ULARGE_INTEGER) == sizeof(FILETIME));
    memcpy(&li, &ft, sizeof(FILETIME));
    li.QuadPart -= 116444736000000000;
    li.QuadPart /= 10000000;
    return (time_t)(li.LowPart);
}

Certainly this will only work if your FILETIME is really in time_t range. I suppose you know what to do with resulting time_t.

32 bit system won't prevent you from reading 64 bit as a binary value. If you prefer scanf you can use "%llu" format.