PVS-Studio warning V547 for ICU

int32_t getRuleWeekInMonth(void) const;

typedef struct _SYSTEMTIME {
  ....
  WORD wDay;
  ....
} SYSTEMTIME, *PSYSTEMTIME;

static UBool getSystemTimeInformation(....)
{
  ....
  standardDate.wDay = std->getRule()->getRuleWeekInMonth();
  if (standardDate.wDay < 0) {
    standardDate.wDay = 5;
  }
  ....
}

This suspicious code was found in ICU project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'standardDate.wDay < 0' is always false. Unsigned type value is never < 0. wintzimpl.cpp 66

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/