-/////////////////////////////////////////////////////////////////////////////
+///////////////////////////////////////////////////////////////////////////////
// Name: wx/datetime.h
// Purpose: implementation of time/date related classes
// Author: Vadim Zeitlin
// Modified by:
// Created: 11.05.99
// RCS-ID: $Id$
-// Copyright: (c) 1998 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
+// Copyright: (c) 1999 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
+// parts of code taken from sndcal library by Scott E. Lee:
+//
+// Copyright 1993-1995, Scott E. Lee, all rights reserved.
+// Permission granted to use, copy, modify, distribute and sell
+// so long as the above copyright and this permission statement
+// are retained in all copies.
+//
// Licence: wxWindows license
-/////////////////////////////////////////////////////////////////////////////
+///////////////////////////////////////////////////////////////////////////////
+
+/*
+ * Implementation notes:
+ *
+ * 1. the time is stored as a 64bit integer containing the signed number of
+ * milliseconds since Jan 1. 1970 (the Unix Epoch) - so it is always
+ * expressed in GMT.
+ *
+ * 2. the range is thus something about 580 million years, but due to current
+ * algorithms limitations, only dates from Nov 24, 4714BC are handled
+ *
+ * 3. standard ANSI C functions are used to do time calculations whenever
+ * possible, i.e. when the date is in the range Jan 1, 1970 to 2038
+ *
+ * 4. otherwise, the calculations are done by converting the date to/from JDN
+ * first (the range limitation mentioned above comes from here: the
+ * algorithm used by Scott E. Lee's code only works for positive JDNs, more
+ * or less)
+ *
+ * 5. the object constructed for the given DD-MM-YYYY HH:MM:SS corresponds to
+ * this moment in local time and may be converted to the object
+ * corresponding to the same date/time in another time zone by using
+ * ToTimezone()
+ *
+ * 6. the conversions to the current (or any other) timezone are done when the
+ * internal time representation is converted to the broken-down one in
+ * wxDateTime::Tm.
+ */
// ============================================================================
// declarations
// (i.e. JDN(Jan 1, 1970) = 2440587.5)
static const int EPOCH_JDN = 2440587;
+// the date of JDN -0.5 (as we don't work with fractional parts, this is the
+// reference date for us) is Nov 24, 4714BC
+static const int JDN_0_YEAR = -4713;
+static const int JDN_0_MONTH = wxDateTime::Nov;
+static const int JDN_0_DAY = 24;
+
+// the constants used for JDN calculations
+static const int JDN_OFFSET = 32046;
+static const int DAYS_PER_5_MONTHS = 153;
+static const int DAYS_PER_4_YEARS = 1461;
+static const int DAYS_PER_400_YEARS = 146097;
+
// ----------------------------------------------------------------------------
// globals
// ----------------------------------------------------------------------------
if ( !s_timezoneSet )
{
- // just call localtime() instead of figurin out whether this system
+ // just call localtime() instead of figuring out whether this system
// supports tzset(), _tzset() or something else
time_t t;
(void)localtime(&t);
}
// return the integral part of the JDN for the midnight of the given date (to
-// get the real JDN you need to add 0.5, this is, in fact, JDN of the noon of
-// the previous day)
+// get the real JDN you need to add 0.5, this is, in fact, JDN of the
+// noon of the previous day)
static long GetTruncatedJDN(wxDateTime::wxDateTime_t day,
wxDateTime::Month mon,
int year)
{
- // CREDIT: the algorithm was taken from Peter Baum's home page
-
- // the algorithm assumes Jan == 1
- int month = mon + 1;
-
- // we want the leap day (Feb 29) be at the end of the year, so we count
- // March as the first month
- if ( month < wxDateTime::Mar + 1 )
+ // CREDIT: code below is by Scott E. Lee (but bugs are mine)
+
+ // check the date validity
+ wxASSERT_MSG(
+ (year > JDN_0_YEAR) ||
+ ((year == JDN_0_YEAR) && (mon > JDN_0_MONTH)) ||
+ ((year == JDN_0_YEAR) && (mon == JDN_0_MONTH) && (day >= JDN_0_DAY)),
+ _T("date out of range - can't convert to JDN")
+ );
+
+ // make the year positive to avoid problems with negative numbers division
+ year += 4800;
+
+ // months are counted from March here
+ int month;
+ if ( mon >= wxDateTime::Mar )
{
- month += MONTHS_IN_YEAR;
- year--;
+ month = mon - 2;
}
-
- // this table contains the number of the days before the 1st of the each
- // month (in a non leap year) with the third value corresponding to March
- // (and the last one to February)
- static const int monthOffsets[14] =
+ else
{
- 0, 31, 61, 92, 122, 153, 184, 214, 245, 275, 306
- };
+ month = mon + 10;
+ year--;
+ }
- // and now add contributions of all terms together to get the result (you'd
- // better see the Web page for the description if you want to understand
- // why it works (if it does :-))
- return day +
- // linear approximation for months
- monthOffsets[month - (wxDateTime::Mar + 1)] +
- // the year contribution
- 365*year + year/4 - year/100 + year/400 +
- // 1721119.5 is the JDN of the midnight of Mar 1, year 0
- 1721118;
+ // now we can simply add all the contributions together
+ return ((year / 100) * DAYS_PER_400_YEARS) / 4
+ + ((year % 100) * DAYS_PER_4_YEARS) / 4
+ + (month * DAYS_PER_5_MONTHS + 2) / 5
+ + day
+ - JDN_OFFSET;
}
// this function is a wrapper around strftime(3)
wday = wxDateTime::Inv_WeekDay;
}
-wxDateTime::Tm::Tm(const struct tm& tm)
+wxDateTime::Tm::Tm(const struct tm& tm, const TimeZone& tz)
+ : m_tz(tz)
{
msec = 0;
sec = tm.tm_sec;
switch ( tz )
{
case wxDateTime::Local:
- // leave offset to be 0
+ // get the offset from C RTL: it returns the difference GMT-local
+ // while we want to have the offset _from_ GMT, hence the '-'
+ m_offset = -GetTimeZone();
break;
case wxDateTime::GMT_12:
case wxDateTime::GMT_3:
case wxDateTime::GMT_2:
case wxDateTime::GMT_1:
- m_offset = -60*(wxDateTime::GMT0 - tz);
+ m_offset = -3600*(wxDateTime::GMT0 - tz);
break;
case wxDateTime::GMT0:
case wxDateTime::GMT10:
case wxDateTime::GMT11:
case wxDateTime::GMT12:
- m_offset = 60*(tz - wxDateTime::GMT0);
+ m_offset = 3600*(tz - wxDateTime::GMT0);
break;
case wxDateTime::A_CST:
// Central Standard Time in use in Australia = UTC + 9.5
- m_offset = 9*60 + 30;
+ m_offset = 60*(9*60 + 30);
break;
default:
// take some arbitrary Sunday
tm tm = { 0, 0, 0, 28, Nov, 99 };
- // and offset it by the number of days needed to get
+ // and offset it by the number of days needed to get the correct wday
tm.tm_mday += wday;
return CallStrftime(abbr ? _T("%a") : _T("%A"), &tm);
// constructors and assignment operators
// ----------------------------------------------------------------------------
-wxDateTime& wxDateTime::Set(const struct tm& tm1)
+// the values in the tm structure contain the local time
+wxDateTime& wxDateTime::Set(const struct tm& tm)
{
wxASSERT_MSG( IsValid(), _T("invalid wxDateTime") );
- tm tm2(tm1);
+ struct tm tm2(tm);
time_t timet = mktime(&tm2);
- if ( timet == (time_t)(-1) )
+
+ if ( timet == (time_t)-1 )
{
- wxFAIL_MSG(_T("Invalid time"));
+ // mktime() rather unintuitively fails for Jan 1, 1970 if the hour is
+ // less than timezone - try to make it work for this case
+ if ( tm2.tm_year == 70 && tm2.tm_mon == 0 && tm2.tm_mday == 1 )
+ {
+ // add timezone to make sure that date is in range
+ tm2.tm_sec -= GetTimeZone();
+
+ timet = mktime(&tm2);
+ if ( timet != (time_t)-1 )
+ {
+ timet += GetTimeZone();
+
+ return Set(timet);
+ }
+ }
+
+ wxFAIL_MSG( _T("mktime() failed") );
return ms_InvDateTime;
}
time_t timet = GetTimeNow();
struct tm *tm = localtime(&timet);
+ wxCHECK_MSG( tm, ms_InvDateTime, _T("localtime() failed") );
+
// adjust the time
tm->tm_hour = hour;
tm->tm_min = minute;
ReplaceDefaultYearMonthWithCurrent(&year, &month);
- wxCHECK_MSG( day <= GetNumberOfDays(month, year), ms_InvDateTime,
+ wxCHECK_MSG( (0 < day) && (day <= GetNumberOfDays(month, year)),
+ ms_InvDateTime,
_T("Invalid date in wxDateTime::Set()") );
// the range of time_t type (inclusive)
tm.tm_hour = hour;
tm.tm_min = minute;
tm.tm_sec = second;
+ tm.tm_isdst = -1; // mktime() will guess it
(void)Set(tm);
m_time -= EPOCH_JDN;
m_time *= SECONDS_PER_DAY * TIME_T_FACTOR;
- Add(wxTimeSpan(hour, minute, second, millisec));
+ // JDN corresponds to GMT, we take localtime
+ Add(wxTimeSpan(hour, minute, second + GetTimeZone(), millisec));
}
return *this;
wxDateTime& wxDateTime::Set(double jdn)
{
- m_time = (jdn - 0.5 - EPOCH_JDN) * TIME_T_FACTOR;
+ // so that m_time will be 0 for the midnight of Jan 1, 1970 which is jdn
+ // EPOCH_JDN + 0.5
+ jdn -= EPOCH_JDN + 0.5;
+
+ m_time = jdn;
+ m_time *= MILLISECONDS_PER_DAY;
return *this;
}
// time_t <-> broken down time conversions
// ----------------------------------------------------------------------------
-wxDateTime::Tm wxDateTime::GetTm() const
+wxDateTime::Tm wxDateTime::GetTm(const TimeZone& tz) const
{
wxASSERT_MSG( IsValid(), _T("invalid wxDateTime") );
if ( time != (time_t)-1 )
{
// use C RTL functions
- tm *tm = localtime(&time);
+ tm *tm;
+ if ( tz.GetOffset() == -GetTimeZone() )
+ {
+ // we are working with local time
+ tm = localtime(&time);
+ }
+ else
+ {
+ time += tz.GetOffset();
+ tm = gmtime(&time);
+ }
// should never happen
- wxCHECK_MSG( tm, Tm(), _T("localtime() failed") );
+ wxCHECK_MSG( tm, Tm(), _T("gmtime() failed") );
- return Tm(*tm);
+ return Tm(*tm, tz);
}
else
{
- // CREDIT: the algorithm was taken from Peter Baum's home page
+ // remember the time and do the calculations with the date only - this
+ // eliminates rounding errors of the floating point arithmetics
+
+ wxLongLong timeMidnight = m_time + tz.GetOffset() * 1000;
+
+ long timeOnly = (timeMidnight % MILLISECONDS_PER_DAY).ToLong();
+
+ // we want to always have positive time and timeMidnight to be really
+ // the midnight before it
+ if ( timeOnly < 0 )
+ {
+ timeOnly = MILLISECONDS_PER_DAY + timeOnly;
+ }
- // calculate the Gregorian date from JDN for the midnight of our date
- wxLongLong timeMidnight = m_time;
- long timeOnly = (m_time % MILLISECONDS_PER_DAY).GetLo();
timeMidnight -= timeOnly;
- // TODO this probably could be optimised somehow...
-
- double jdn = (timeMidnight / MILLISECONDS_PER_DAY).GetLo();
- jdn += EPOCH_JDN + 0.5;
- long z = jdn - 1721118.5;
- double r = jdn - 1721118.5 - z;
- double g = z - 0.25;
- long a = g/36524.25; // number of days per year
- long b = a - a / 4;
- int year = (b + g) / 365.25;
- long c = b + z - 365.25*year;
- int month = (5*c + 456)/153;
- int day = c - (153*month - 457)/5 + (r < 0.5 ? 0 : 1);
- if ( month > 12 )
+ // calculate the Gregorian date from JDN for the midnight of our date:
+ // this will yield day, month (in 1..12 range) and year
+
+ // actually, this is the JDN for the noon of the previous day
+ long jdn = (timeMidnight / MILLISECONDS_PER_DAY).ToLong() + EPOCH_JDN;
+
+ // CREDIT: code below is by Scott E. Lee (but bugs are mine)
+
+ wxASSERT_MSG( jdn > -2, _T("JDN out of range") );
+
+ // calculate the century
+ int temp = (jdn + JDN_OFFSET) * 4 - 1;
+ int century = temp / DAYS_PER_400_YEARS;
+
+ // then the year and day of year (1 <= dayOfYear <= 366)
+ temp = ((temp % DAYS_PER_400_YEARS) / 4) * 4 + 3;
+ int year = (century * 100) + (temp / DAYS_PER_4_YEARS);
+ int dayOfYear = (temp % DAYS_PER_4_YEARS) / 4 + 1;
+
+ // and finally the month and day of the month
+ temp = dayOfYear * 5 - 3;
+ int month = temp / DAYS_PER_5_MONTHS;
+ int day = (temp % DAYS_PER_5_MONTHS) / 5 + 1;
+
+ // month is counted from March - convert to normal
+ if ( month < 10 )
+ {
+ month += 3;
+ }
+ else
{
- year++;
- month -= 12;
+ year += 1;
+ month -= 9;
}
+ // year is offset by 4800
+ year -= 4800;
+
+ // check that the algorithm gave us something reasonable
+ wxASSERT_MSG( (0 < month) && (month <= 12), _T("invalid month") );
+ wxASSERT_MSG( (1 <= day) && (day < 32), _T("invalid day") );
+ wxASSERT_MSG( (INT_MIN <= year) && (year <= INT_MAX),
+ _T("year range overflow") );
+
+ // construct Tm from these values
Tm tm;
- tm.year = year;
+ tm.year = (int)year;
tm.mon = (Month)(month - 1); // algorithm yields 1 for January, not 0
- tm.mday = day;
+ tm.mday = (wxDateTime_t)day;
tm.msec = timeOnly % 1000;
timeOnly -= tm.msec;
timeOnly /= 1000; // now we have time in seconds
double wxDateTime::GetJulianDayNumber() const
{
- Tm tm(GetTm());
+ // JDN are always expressed for the GMT dates
+ Tm tm(ToTimezone(GMT0).GetTm(GMT0));
double result = GetTruncatedJDN(tm.mday, tm.mon, tm.year);
}
// ----------------------------------------------------------------------------
-// timezone stuff
+// timezone and DST stuff
// ----------------------------------------------------------------------------
-wxDateTime& wxDateTime::MakeUTC()
+int wxDateTime::IsDST(wxDateTime::Country country) const
{
- return Add(wxTimeSpan::Seconds(GetTimeZone()));
+ wxCHECK_MSG( country == Country_Default, -1,
+ _T("country support not implemented") );
+
+ // use the C RTL for the dates in the standard range
+ time_t timet = GetTicks();
+ if ( timet != (time_t)-1 )
+ {
+ tm *tm = localtime(&timet);
+
+ wxCHECK_MSG( tm, -1, _T("localtime() failed") );
+
+ return tm->tm_isdst;
+ }
+ else
+ {
+ // wxFAIL_MSG( _T("TODO") );
+
+ return -1;
+ }
}
wxDateTime& wxDateTime::MakeTimezone(const TimeZone& tz)
{
- int minDiff = GetTimeZone() / SECONDS_IN_MINUTE + tz.GetOffset();
- return Add(wxTimeSpan::Minutes(minDiff));
-}
+ int secDiff = GetTimeZone() + tz.GetOffset();
-wxDateTime& wxDateTime::MakeLocalTime(const TimeZone& tz)
-{
- int minDiff = GetTimeZone() / SECONDS_IN_MINUTE + tz.GetOffset();
- return Substract(wxTimeSpan::Minutes(minDiff));
+ // we need to know whether DST is or not in effect for this date
+ if ( IsDST() == 1 )
+ {
+ // FIXME we assume that the DST is always shifted by 1 hour
+ secDiff -= 3600;
+ }
+
+ return Substract(wxTimeSpan::Seconds(secDiff));
}
// ----------------------------------------------------------------------------
// wxDateTime to/from text representations
// ----------------------------------------------------------------------------
-wxString wxDateTime::Format(const wxChar *format) const
+wxString wxDateTime::Format(const wxChar *format, const TimeZone& tz) const
{
wxCHECK_MSG( format, _T(""), _T("NULL format in wxDateTime::Format") );
if ( time != (time_t)-1 )
{
// use strftime()
- tm *tm = localtime(&time);
+ tm *tm;
+ if ( tz.GetOffset() == -GetTimeZone() )
+ {
+ // we are working with local time
+ tm = localtime(&time);
+ }
+ else
+ {
+ time += tz.GetOffset();
+
+ tm = gmtime(&time);
+ }
// should never happen
- wxCHECK_MSG( tm, _T(""), _T("localtime() failed") );
+ wxCHECK_MSG( tm, _T(""), _T("gmtime() failed") );
return CallStrftime(format, tm);
}
// the real year modulo 28 (so the week days coincide for them)
// find the YEAR
- int yearReal = GetYear();
+ int yearReal = GetYear(tz);
int year = 1970 + yearReal % 28;
wxString strYear;
// use strftime() to format the same date but in supported year
wxDateTime dt(*this);
dt.SetYear(year);
- wxString str = dt.Format(format);
+ wxString str = dt.Format(format, tz);
// now replace the occurence of 1999 with the real year
wxString strYearReal;
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