Converts a Win32 FileTime into a POSIX LONGLONG Timestamp. Credit (https://www.frenk.com/2009/12/convert-filetime-to-unix-timestamp/)

Win32_FileTime_to_POSIX.c

// Converts a windows FILETIME structure to a POSIX timestamp
// https://www.frenk.com/2009/12/convert-filetime-to-unix-timestamp/
LONGLONG FileTime_to_POSIX(FILETIME ft)
{
	// takes the last modified date
	LARGE_INTEGER date, adjust;
	date.HighPart = ft.dwHighDateTime;
	date.LowPart = ft.dwLowDateTime;

	// 100-nanoseconds = milliseconds * 10000
	adjust.QuadPart = 11644473600000 * 10000;

	// removes the diff between 1970 and 1601
	date.QuadPart -= adjust.QuadPart;

	// converts back from 100-nanoseconds to seconds
	return date.QuadPart / 10000000;
}