windows-server-2003/inetcore/urlmon/utils/coletime.cxx

#include <urlint.h>
#include <map_kv.h>
#include "coll.hxx"
#include "coletime.hxx"
#include <math.h>


/////////////////////////////////////////////////////////////////////////////
// COleDateTime class HELPER definitions

// Verifies will fail if the needed buffer size is too large
#define MAX_TIME_BUFFER_SIZE    128         // matches that in timecore.cpp
#define MIN_DATE                (-657434L)  // about year 100
#define MAX_DATE                2958465L    // about year 9999

// Half a second, expressed in days
#define HALF_SECOND  (1.0/172800.0)

// One-based array of days in year at month start
static int rgMonthDays[13] =
{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};

static BOOL OleDateFromTm(WORD wYear, WORD wMonth, WORD wDay,
                          WORD wHour, WORD wMinute, WORD wSecond, DATE& dtDest);
static BOOL TmFromOleDate(DATE dtSrc, struct tm& tmDest);
static void TmConvertToStandardFormat(struct tm& tmSrc);
static double DoubleFromDate(DATE dt);
static DATE DateFromDouble(double dbl);

/////////////////////////////////////////////////////////////////////////////
// COleDateTime class

COleDateTime PASCAL COleDateTime::GetCurrentTime()
{
    return COleDateTime(::time(NULL));
}

int COleDateTime::GetYear() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_year;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetMonth() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_mon;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetDay() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_mday;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetHour() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_hour;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetMinute() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_min;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetSecond() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_sec;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetDayOfWeek() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_wday;
    else
        return AFX_OLE_DATETIME_ERROR;
}

int COleDateTime::GetDayOfYear() const
{
    struct tm tmTemp;

    if (GetStatus() == valid && TmFromOleDate(m_dt, tmTemp))
        return tmTemp.tm_yday;
    else
        return AFX_OLE_DATETIME_ERROR;
}

#ifdef _not_this_
const COleDateTime& COleDateTime::operator=(const VARIANT& varSrc)
{
    if (varSrc.vt != VT_DATE)
    {
        TRY
        {
            COleVariant varTemp(varSrc);
            varTemp.ChangeType(VT_DATE);
            m_dt = varTemp.date;
            SetStatus(valid);
        }
        // Catch COleException from ChangeType, but not CMemoryException
        CATCH(COleException, e)
        {
            // Not able to convert VARIANT to DATE
            DELETE_EXCEPTION(e);
            m_dt = 0;
            SetStatus(invalid);
        }
        END_CATCH
    }
    else
    {
        m_dt = varSrc.date;
        SetStatus(valid);
    }

    return *this;
}
#endif //_not_this_

const COleDateTime& COleDateTime::operator=(DATE dtSrc)
{
    m_dt = dtSrc;
    SetStatus(valid);

    return *this;
}

const COleDateTime& COleDateTime::operator=(const time_t& timeSrc)
{
    // Convert time_t to struct tm
    tm *ptm = localtime(&timeSrc);

    if (ptm != NULL)
    {
        m_status = OleDateFromTm((WORD)ptm->tm_year + 1900,
                                 (WORD)(ptm->tm_mon + 1), (WORD)ptm->tm_mday,
                                 (WORD)ptm->tm_hour, (WORD)ptm->tm_min,
                                 (WORD)ptm->tm_sec, m_dt) ? valid : invalid;
    }
    else
    {
        // Local time must have failed (timsSrc before 1/1/70 12am)
        SetStatus(invalid);
        ASSERT(FALSE);
    }

    return *this;
}

const COleDateTime& COleDateTime::operator=(const SYSTEMTIME& systimeSrc)
{
    m_status = OleDateFromTm(systimeSrc.wYear, systimeSrc.wMonth,
                             systimeSrc.wDay, systimeSrc.wHour, systimeSrc.wMinute,
                             systimeSrc.wSecond, m_dt) ? valid : invalid;

    return *this;
}

const COleDateTime& COleDateTime::operator=(const FILETIME& filetimeSrc)
{
    // Assume UTC FILETIME, so convert to LOCALTIME
    FILETIME filetimeLocal;
    if (!FileTimeToLocalFileTime( &filetimeSrc, &filetimeLocal))
    {
#ifdef _DEBUG
        DWORD dwError = GetLastError();
        TRACE1("\nFileTimeToLocalFileTime failed. Error = %lu.\n\t", dwError);
#endif // _DEBUG
        m_status = invalid;
    }
    else
    {
        // Take advantage of SYSTEMTIME -> FILETIME conversion
        SYSTEMTIME systime;
        m_status = FileTimeToSystemTime(&filetimeLocal, &systime) ?
                   valid : invalid;

        // At this point systime should always be valid, but...
        if (GetStatus() == valid)
        {
            m_status = OleDateFromTm(systime.wYear, systime.wMonth,
                                     systime.wDay, systime.wHour, systime.wMinute,
                                     systime.wSecond, m_dt) ? valid : invalid;
        }
    }

    return *this;
}

BOOL COleDateTime::operator<(const COleDateTime& date) const
{
    ASSERT(GetStatus() == valid);
    ASSERT(date.GetStatus() == valid);

    // Handle negative dates
    return DoubleFromDate(m_dt) < DoubleFromDate(date.m_dt);
}

BOOL COleDateTime::operator>(const COleDateTime& date) const
{   ASSERT(GetStatus() == valid);
    ASSERT(date.GetStatus() == valid);

    // Handle negative dates
    return DoubleFromDate(m_dt) > DoubleFromDate(date.m_dt);
}

BOOL COleDateTime::operator<=(const COleDateTime& date) const
{
    ASSERT(GetStatus() == valid);
    ASSERT(date.GetStatus() == valid);

    // Handle negative dates
    return DoubleFromDate(m_dt) <= DoubleFromDate(date.m_dt);
}

BOOL COleDateTime::operator>=(const COleDateTime& date) const
{
    ASSERT(GetStatus() == valid);
    ASSERT(date.GetStatus() == valid);

    // Handle negative dates
    return DoubleFromDate(m_dt) >= DoubleFromDate(date.m_dt);
}

COleDateTime COleDateTime::operator+(const COleDateTimeSpan& dateSpan) const
{
    COleDateTime dateResult;    // Initializes m_status to valid

    // If either operand NULL, result NULL
    if (GetStatus() == null || dateSpan.GetStatus() == null)
    {
        dateResult.SetStatus(null);
        return dateResult;
    }

    // If either operand invalid, result invalid
    if (GetStatus() == invalid || dateSpan.GetStatus() == invalid)
    {
        dateResult.SetStatus(invalid);
        return dateResult;
    }

    // Compute the actual date difference by adding underlying dates
    dateResult = DateFromDouble(DoubleFromDate(m_dt) + dateSpan.m_span);

    // Validate within range
    dateResult.CheckRange();

    return dateResult;
}

COleDateTime COleDateTime::operator-(const COleDateTimeSpan& dateSpan) const
{
    COleDateTime dateResult;    // Initializes m_status to valid

    // If either operand NULL, result NULL
    if (GetStatus() == null || dateSpan.GetStatus() == null)
    {
        dateResult.SetStatus(null);
        return dateResult;
    }

    // If either operand invalid, result invalid
    if (GetStatus() == invalid || dateSpan.GetStatus() == invalid)
    {
        dateResult.SetStatus(invalid);
        return dateResult;
    }

    // Compute the actual date difference by subtracting underlying dates
    dateResult = DateFromDouble(DoubleFromDate(m_dt) - dateSpan.m_span);

    // Validate within range
    dateResult.CheckRange();

    return dateResult;
}

COleDateTimeSpan COleDateTime::operator-(const COleDateTime& date) const
{
    COleDateTimeSpan spanResult;

    // If either operand NULL, result NULL
    if (GetStatus() == null || date.GetStatus() == null)
    {
        spanResult.SetStatus(COleDateTimeSpan::null);
        return spanResult;
    }

    // If either operand invalid, result invalid
    if (GetStatus() == invalid || date.GetStatus() == invalid)
    {
        spanResult.SetStatus(COleDateTimeSpan::invalid);
        return spanResult;
    }

    // Return result (span can't be invalid, so don't check range)
    return DoubleFromDate(m_dt) - DoubleFromDate(date.m_dt);
}

BOOL COleDateTime::SetDateTime(int nYear, int nMonth, int nDay,
                               int nHour, int nMin, int nSec)
{
    return m_status = OleDateFromTm((WORD)nYear, (WORD)nMonth,
                                    (WORD)nDay, (WORD)nHour, (WORD)nMin, (WORD)nSec, m_dt) ?
                      valid : invalid;
}

#ifdef _not_yet_
BOOL COleDateTime::ParseDateTime(LPCTSTR lpszDate, DWORD dwFlags, LCID lcid)
{
    USES_CONVERSION;
    CString strDate = lpszDate;

    SCODE sc;
    if (FAILED(sc = VarDateFromStr((LPOLESTR)T2COLE(strDate), lcid,
                                   dwFlags, &m_dt)))
    {
        if (sc == DISP_E_TYPEMISMATCH)
        {
            // Can't convert string to date, set 0 and invalidate
            m_dt = 0;
            SetStatus(invalid);
            return FALSE;
        }
        else if (sc == DISP_E_OVERFLOW)
        {
            // Can't convert string to date, set -1 and invalidate
            m_dt = -1;
            SetStatus(invalid);
            return FALSE;
        }
        else
        {
            TRACE0("\nCOleDateTime VarDateFromStr call failed.\n\t");
            if (sc == E_OUTOFMEMORY)
                AfxThrowMemoryException();
            else
                AfxThrowOleException(sc);
        }
    }

    SetStatus(valid);
    return TRUE;
}

CString COleDateTime::Format(DWORD dwFlags, LCID lcid) const
{
    USES_CONVERSION;
    CString strDate;

    // If null, return empty string
    if (GetStatus() == null)
        return strDate;

    // If invalid, return DateTime resource string
    if (GetStatus() == invalid)
    {
        VERIFY(strDate.LoadString(AFX_IDS_INVALID_DATETIME));
        return strDate;
    }

    COleVariant var;
    // Don't need to trap error. Should not fail due to type mismatch
    CheckError(VarBstrFromDate(m_dt, lcid, dwFlags, &V_BSTR(&var)));
    var.vt = VT_BSTR;
    return OLE2CT(V_BSTR(&var));
}
#endif //_not_yet_

CString COleDateTime::Format(LPCTSTR pFormat) const
{
    CString strDate;
    struct tm tmTemp;

    // If null, return empty string
    if (GetStatus() == null)
        return strDate;

    // If invalid, return DateTime resource string
    if (GetStatus() == invalid || !TmFromOleDate(m_dt, tmTemp))
    {
        //VERIFY(strDate.LoadString(AFX_IDS_INVALID_DATETIME));
        return strDate;
    }

    // Convert tm from afx internal format to standard format
    TmConvertToStandardFormat(tmTemp);

    // Fill in the buffer, disregard return value as it's not necessary
    LPTSTR lpszTemp = strDate.GetBufferSetLength(MAX_TIME_BUFFER_SIZE);
    _tcsftime(lpszTemp, strDate.GetLength(), pFormat, &tmTemp);
    strDate.ReleaseBuffer();

    return strDate;
}

CString COleDateTime::Format(UINT nFormatID) const
{
    CString strFormat;
    //VERIFY(strFormat.LoadString(nFormatID) != 0);
    return Format(strFormat);
}

void COleDateTime::CheckRange()
{
    if (m_dt > MAX_DATE || m_dt < MIN_DATE) // about year 100 to about 9999
        SetStatus(invalid);
}

// serialization
#ifdef _DEBUG
CDumpContext& AFXAPI operator<<(CDumpContext& dc, COleDateTime dateSrc)
{
    dc << "\nCOleDateTime Object:";
    dc << "\n\tm_status = " << (long)dateSrc.m_status;

    COleVariant var(dateSrc);
    var.ChangeType(VT_BSTR);

    return dc << "\n\tdate = " << (LPCTSTR)var.bstrVal;
}
#endif // _DEBUG

#ifdef _not_yet_
CArchive& AFXAPI operator<<(CArchive& ar, COleDateTime dateSrc)
{
    ar << (long)dateSrc.m_status;
    return ar << dateSrc.m_dt;
}

CArchive& AFXAPI operator>>(CArchive& ar, COleDateTime& dateSrc)
{
    ar >> (long&)dateSrc.m_status;
    return ar >> dateSrc.m_dt;
}
#endif //_not_yet_

/////////////////////////////////////////////////////////////////////////////
// COleDateTimeSpan class helpers

#define MAX_DAYS_IN_SPAN    3615897L

/////////////////////////////////////////////////////////////////////////////
// COleDateTimeSpan class
long COleDateTimeSpan::GetHours() const
{
    ASSERT(GetStatus() == valid);

    double dblTemp;

    // Truncate days and scale up
    dblTemp = modf(m_span, &dblTemp);
    return (long)(dblTemp * 24);
}

long COleDateTimeSpan::GetMinutes() const
{
    ASSERT(GetStatus() == valid);

    double dblTemp;

    // Truncate hours and scale up
    dblTemp = modf(m_span * 24, &dblTemp);
    return (long)(dblTemp * 60);
}

long COleDateTimeSpan::GetSeconds() const
{
    ASSERT(GetStatus() == valid);

    double dblTemp;

    // Truncate minutes and scale up
    dblTemp = modf(m_span * 24 * 60, &dblTemp);
    return (long)(dblTemp * 60);
}

const COleDateTimeSpan& COleDateTimeSpan::operator=(double dblSpanSrc)
{
    m_span = dblSpanSrc;
    SetStatus(valid);
    return *this;
}

const COleDateTimeSpan& COleDateTimeSpan::operator=(const COleDateTimeSpan& dateSpanSrc)
{
    m_span = dateSpanSrc.m_span;
    m_status = dateSpanSrc.m_status;
    return *this;
}

COleDateTimeSpan COleDateTimeSpan::operator+(const COleDateTimeSpan& dateSpan) const
{
    COleDateTimeSpan dateSpanTemp;

    // If either operand Null, result Null
    if (GetStatus() == null || dateSpan.GetStatus() == null)
    {
        dateSpanTemp.SetStatus(null);
        return dateSpanTemp;
    }

    // If either operand Invalid, result Invalid
    if (GetStatus() == invalid || dateSpan.GetStatus() == invalid)
    {
        dateSpanTemp.SetStatus(invalid);
        return dateSpanTemp;
    }

    // Add spans and validate within legal range
    dateSpanTemp.m_span = m_span + dateSpan.m_span;
    dateSpanTemp.CheckRange();

    return dateSpanTemp;
}

COleDateTimeSpan COleDateTimeSpan::operator-(const COleDateTimeSpan& dateSpan) const
{
    COleDateTimeSpan dateSpanTemp;

    // If either operand Null, result Null
    if (GetStatus() == null || dateSpan.GetStatus() == null)
    {
        dateSpanTemp.SetStatus(null);
        return dateSpanTemp;
    }

    // If either operand Invalid, result Invalid
    if (GetStatus() == invalid || dateSpan.GetStatus() == invalid)
    {
        dateSpanTemp.SetStatus(invalid);
        return dateSpanTemp;
    }

    // Subtract spans and validate within legal range
    dateSpanTemp.m_span = m_span - dateSpan.m_span;
    dateSpanTemp.CheckRange();

    return dateSpanTemp;
}

void COleDateTimeSpan::SetDateTimeSpan(
                                      long lDays, int nHours, int nMins, int nSecs)
{
    // Set date span by breaking into fractional days (all input ranges valid)
    m_span = lDays + ((double)nHours)/24 + ((double)nMins)/(24*60) +
             ((double)nSecs)/(24*60*60);

    SetStatus(valid);
}

CString COleDateTimeSpan::Format(LPCTSTR pFormat) const
{
    CString strSpan;
    struct tm tmTemp;

    // If null, return empty string
    if (GetStatus() == null)
        return strSpan;

    // If invalid, return DateTimeSpan resource string
    if (GetStatus() == invalid || !TmFromOleDate(m_span, tmTemp))
    {
        //VERIFY(strSpan.LoadString(AFX_IDS_INVALID_DATETIMESPAN));
        return strSpan;
    }

    // Convert tm from afx internal format to standard format
    TmConvertToStandardFormat(tmTemp);

    // Fill in the buffer, disregard return value as it's not necessary
    LPTSTR lpszTemp = strSpan.GetBufferSetLength(MAX_TIME_BUFFER_SIZE);
    _tcsftime(lpszTemp, strSpan.GetLength(), pFormat, &tmTemp);
    strSpan.ReleaseBuffer();

    return strSpan;
}

CString COleDateTimeSpan::Format(UINT nFormatID) const
{
    CString strFormat;
    //VERIFY(strFormat.LoadString(nFormatID) != 0);
    return Format(strFormat);
}

void COleDateTimeSpan::CheckRange()
{
    if (m_span < -MAX_DAYS_IN_SPAN || m_span > MAX_DAYS_IN_SPAN)
        SetStatus(invalid);
}

// serialization
#ifdef _DEBUG
CDumpContext& AFXAPI operator<<(CDumpContext& dc, COleDateTimeSpan dateSpanSrc)
{
    dc << "\nCOleDateTimeSpan Object:";
    dc << "\n\tm_status = " << (long)dateSpanSrc.m_status;

    COleVariant var(dateSpanSrc.m_span);
    var.ChangeType(VT_BSTR);

    return dc << "\n\tdateSpan = " << (LPCTSTR)var.bstrVal;
}
#endif // _DEBUG

#ifdef _not_yet_
CArchive& AFXAPI operator<<(CArchive& ar, COleDateTimeSpan dateSpanSrc)
{
    ar << (long)dateSpanSrc.m_status;
    return ar << dateSpanSrc.m_span;
}

CArchive& AFXAPI operator>>(CArchive& ar, COleDateTimeSpan& dateSpanSrc)
{
    ar >> (long&)dateSpanSrc.m_status;
    return ar >> dateSpanSrc.m_span;
}
#endif //_not_yet_

/////////////////////////////////////////////////////////////////////////////
// COleDateTime class HELPERS - implementation

BOOL OleDateFromTm(WORD wYear, WORD wMonth, WORD wDay,
                   WORD wHour, WORD wMinute, WORD wSecond, DATE& dtDest)
{
    // Validate year and month (ignore day of week and milliseconds)
    if (wYear > 9999 || wMonth < 1 || wMonth > 12)
        return FALSE;

    //  Check for leap year and set the number of days in the month
    BOOL bLeapYear = ((wYear & 3) == 0) &&
                     ((wYear % 100) != 0 || (wYear % 400) == 0);

    int nDaysInMonth =
    rgMonthDays[wMonth] - rgMonthDays[wMonth-1] +
    ((bLeapYear && wDay == 29 && wMonth == 2) ? 1 : 0);

    // Finish validating the date
    if (wDay < 1 || wDay > nDaysInMonth ||
        wHour > 23 || wMinute > 59 ||
        wSecond > 59)
    {
        return FALSE;
    }

    // Cache the date in days and time in fractional days
    long nDate;
    double dblTime;

    //It is a valid date; make Jan 1, 1AD be 1
    nDate = wYear*365L + wYear/4 - wYear/100 + wYear/400 +
            rgMonthDays[wMonth-1] + wDay;

    //  If leap year and it's before March, subtract 1:
    if (wMonth <= 2 && bLeapYear)
        --nDate;

    //  Offset so that 12/30/1899 is 0
    nDate -= 693959L;

    dblTime = (((long)wHour * 3600L) +  // hrs in seconds
               ((long)wMinute * 60L) +  // mins in seconds
               ((long)wSecond)) / 86400.;

    dtDest = (double) nDate + ((nDate >= 0) ? dblTime : -dblTime);

    return TRUE;
}

BOOL TmFromOleDate(DATE dtSrc, struct tm& tmDest)
{
    // The legal range does not actually span year 0 to 9999.
    if (dtSrc > MAX_DATE || dtSrc < MIN_DATE) // about year 100 to about 9999
        return FALSE;

    long nDays;             // Number of days since Dec. 30, 1899
    long nDaysAbsolute;     // Number of days since 1/1/0
    long nSecsInDay;        // Time in seconds since midnight
    long nMinutesInDay;     // Minutes in day

    long n400Years;         // Number of 400 year increments since 1/1/0
    long n400Century;       // Century within 400 year block (0,1,2 or 3)
    long n4Years;           // Number of 4 year increments since 1/1/0
    long n4Day;             // Day within 4 year block
    //  (0 is 1/1/yr1, 1460 is 12/31/yr4)
    long n4Yr;              // Year within 4 year block (0,1,2 or 3)
    BOOL bLeap4 = TRUE;     // TRUE if 4 year block includes leap year

    double dblDate = dtSrc; // tempory serial date

    // If a valid date, then this conversion should not overflow
    nDays = (long)dblDate;

    // Round to the second
    dblDate += ((dtSrc > 0.0) ? HALF_SECOND : -HALF_SECOND);

    nDaysAbsolute = (long)dblDate + 693959L; // Add days from 1/1/0 to 12/30/1899

    dblDate = fabs(dblDate);
    nSecsInDay = (long)((dblDate - floor(dblDate)) * 86400.);

    // Calculate the day of week (sun=1, mon=2...)
    //   -1 because 1/1/0 is Sat.  +1 because we want 1-based
    tmDest.tm_wday = (int)((nDaysAbsolute - 1) % 7L) + 1;

    // Leap years every 4 yrs except centuries not multiples of 400.
    n400Years = (long)(nDaysAbsolute / 146097L);

    // Set nDaysAbsolute to day within 400-year block
    nDaysAbsolute %= 146097L;

    // -1 because first century has extra day
    n400Century = (long)((nDaysAbsolute - 1) / 36524L);

    // Non-leap century
    if (n400Century != 0)
    {
        // Set nDaysAbsolute to day within century
        nDaysAbsolute = (nDaysAbsolute - 1) % 36524L;

        // +1 because 1st 4 year increment has 1460 days
        n4Years = (long)((nDaysAbsolute + 1) / 1461L);

        if (n4Years != 0)
            n4Day = (long)((nDaysAbsolute + 1) % 1461L);
        else
        {
            bLeap4 = FALSE;
            n4Day = (long)nDaysAbsolute;
        }
    }
    else
    {
        // Leap century - not special case!
        n4Years = (long)(nDaysAbsolute / 1461L);
        n4Day = (long)(nDaysAbsolute % 1461L);
    }

    if (bLeap4)
    {
        // -1 because first year has 366 days
        n4Yr = (n4Day - 1) / 365;

        if (n4Yr != 0)
            n4Day = (n4Day - 1) % 365;
    }
    else
    {
        n4Yr = n4Day / 365;
        n4Day %= 365;
    }

    // n4Day is now 0-based day of year. Save 1-based day of year, year number
    tmDest.tm_yday = (int)n4Day + 1;
    tmDest.tm_year = n400Years * 400 + n400Century * 100 + n4Years * 4 + n4Yr;

    // Handle leap year: before, on, and after Feb. 29.
    if (n4Yr == 0 && bLeap4)
    {
        // Leap Year
        if (n4Day == 59)
        {
            /* Feb. 29 */
            tmDest.tm_mon = 2;
            tmDest.tm_mday = 29;
            goto DoTime;
        }

        // Pretend it's not a leap year for month/day comp.
        if (n4Day >= 60)
            --n4Day;
    }

    // Make n4DaY a 1-based day of non-leap year and compute
    //  month/day for everything but Feb. 29.
    ++n4Day;

    // Month number always >= n/32, so save some loop time */
    for (tmDest.tm_mon = (n4Day >> 5) + 1;
        n4Day > rgMonthDays[tmDest.tm_mon]; tmDest.tm_mon++);

    tmDest.tm_mday = (int)(n4Day - rgMonthDays[tmDest.tm_mon-1]);

    DoTime:
    if (nSecsInDay == 0)
        tmDest.tm_hour = tmDest.tm_min = tmDest.tm_sec = 0;
    else
    {
        tmDest.tm_sec = (int)nSecsInDay % 60L;
        nMinutesInDay = nSecsInDay / 60L;
        tmDest.tm_min = (int)nMinutesInDay % 60;
        tmDest.tm_hour = (int)nMinutesInDay / 60;
    }

    return TRUE;
}

void TmConvertToStandardFormat(struct tm& tmSrc)
{
    // Convert afx internal tm to format expected by runtimes (_tcsftime, etc)
    tmSrc.tm_year -= 1900;  // year is based on 1900
    tmSrc.tm_mon -= 1;      // month of year is 0-based
    tmSrc.tm_wday -= 1;     // day of week is 0-based
    tmSrc.tm_yday -= 1;     // day of year is 0-based
}

double DoubleFromDate(DATE dt)
{
    // No problem if positive
    if (dt >= 0)
        return dt;

    // If negative, must convert since negative dates not continuous
    // (examples: -1.25 to -.75, -1.50 to -.50, -1.75 to -.25)
    double temp = ceil(dt);
    return temp - (dt - temp);
}

DATE DateFromDouble(double dbl)
{
    // No problem if positive
    if (dbl >= 0)
        return dbl;

    // If negative, must convert since negative dates not continuous
    // (examples: -.75 to -1.25, -.50 to -1.50, -.25 to -1.75)
    double temp = floor(dbl); // dbl is now whole part
    return temp + (temp - dbl);
}