Question

i am trying to format a date using Windows GetDateFormat API function:

nResult = GetDateFormat(
      localeId,   //0x409 for en-US, or LOCALE_USER_DEFAULT if you're not testing
      0,          //flags
      dt,         //a SYSTEMTIME structure
      "M/d/yyyy", //the format we require
      null,       //the output buffer to contain string (null for now while we get the length)
      0);         //the length of the output buffer (zero while we get the length)

Now we pass it a date/time:

SYSTEMTIME dt;
dt.wYear = 1600;
dt.wMonth = 12;
dt.wDay = 31;

In this case nResult returns zero:

The function returns 0 if it does not succeed. To get extended error information, the application can call GetLastError, which can return one of the following error codes:

• ERROR_INSUFFICIENT_BUFFER. A supplied buffer size was not large enough, or it was incorrectly set to NULL.
• ERROR_INVALID_FLAGS. The values supplied for flags were not valid.
• ERROR_INVALID_PARAMETER. Any of the parameter values was invalid.

If, however, i return a date one day later:

SYSTEMTIME dt;
dt.wYear = 1601;
dt.wMonth = 1;
dt.wDay = 1;

Then it works.

What am i doing wrong? How do i format dates?

e.g. the date of the birth of Christ:

12/25/0000

or the date when the universe started:

-10/22/4004 6:00 PM

or the date Caesar died:

-3/15/44

---

Bonus Reading

• Sorting It All Out: GetDateFormat is Gregorian based
• GetDateFormatEx function

Answer 1

This is actually a limitation on SystemTime.

...year/month/day/hour/minute/second/milliseconds value since 1 January 1601 00:00:00 UT... to 31 December 30827 23:59:59.999

I spent some time looking up how to get around this limitation, but since GetDateFormat() takes a SystemTime you’ll probably have to bite the bullet and write your own format() method.