Fix support for dates after 2038 in wxDateTime with 64-bit time_t

Use CRT for dates > 2038 in wxDateTime::Set() if time_t is 64-bit.

See wxWidgets#24464.

Co-authored-by: Vadim Zeitlin <vadim@wxwidgets.org>

docs/changes.txt

@@ -254,6 +254,7 @@ Changes in behaviour which may result in build errors
 All:
 
 - Add support for "%F" format specifier to wxDateTime (#24173).
+- Support dates > 2038 if time_t is 64-bit (Lauri Nurmi, #24464).
 - Restore possible ABI incompatibility with wx < 3.2.3 in wxString.
 - Set request and response for wxEVT_WEBREQUEST_DATA events (#24416).
 

include/wx/datetime.h

@@ -1621,9 +1621,11 @@ class WXDLLIMPEXP_BASE wxDateTimeWorkDays : public wxDateTimeHolidayAuthority
 
 inline bool wxDateTime::IsInStdRange() const
 {
-    // currently we don't know what is the real type of time_t so prefer to err
-    // on the safe side and limit it to 32 bit values which is safe everywhere
-    return m_time >= 0l && (m_time / TIME_T_FACTOR) < wxINT32_MAX;
+    // if sizeof(time_t) is greater than 32 bits, we assume it
+    // is safe to return values exceeding wxINT32_MAX
+
+    return m_time >= 0l &&
+        ( (sizeof(time_t) > 4 ) || ( (m_time / TIME_T_FACTOR) < wxINT32_MAX) );
 }
 
 /* static */
@@ -1730,7 +1732,7 @@ inline time_t wxDateTime::GetTicks() const
         return (time_t)-1;
     }
 
-    return (time_t)((m_time / (long)TIME_T_FACTOR).ToLong()) + WX_TIME_BASE_OFFSET;
+    return (time_t)((m_time / TIME_T_FACTOR).GetValue()) + WX_TIME_BASE_OFFSET;
 }
 
 inline bool wxDateTime::SetToLastWeekDay(WeekDay weekday,

src/common/datetime.cpp

@@ -27,7 +27,8 @@
  *    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
+ *    possible, i.e. when the date is in time_t range, i.e. after Jan 1, 1970
+ *    and, for 32-bit time_t, before 2038.
  *
  * 4. otherwise, the calculations are done by converting the date to/from JDN
  *    first (the range limitation mentioned above comes from here: the
@@ -1257,13 +1258,18 @@ wxDateTime& wxDateTime::Set(wxDateTime_t day,
     wxDATETIME_CHECK( (0 < day) && (day <= GetNumberOfDays(month, year)),
                       wxT("Invalid date in wxDateTime::Set()") );
 
-    // the range of time_t type (inclusive)
+    // Check if we can use the standard library implementation: this only works
+    // for the dates representable by time_t, i.e. after the beginning of the
+    // Epoch and, for 32-bit time_t, before 2038 (for 64-bit time_t, the range
+    // is unlimited and while we can't be sure that the standard library works
+    // for the dates in the distant future, we are not going to do better
+    // ourselves neither, so let it handle them).
     static const int yearMinInRange = 1970;
     static const int yearMaxInRange = 2037;
 
     // test only the year instead of testing for the exact end of the Unix
     // time_t range - it doesn't bring anything to do more precise checks
-    if ( year >= yearMinInRange && year <= yearMaxInRange )
+    if ( year >= yearMinInRange && (sizeof(time_t) > 4 || year <= yearMaxInRange) )
     {
         // use the standard library version if the date is in range - this is
         // probably more efficient than our code

tests/datetime/datetimetest.cpp

@@ -127,7 +127,7 @@ struct Date
     wxDateTime::wxDateTime_t hour, min, sec;
     double jdn;
     wxDateTime::WeekDay wday;
-    time_t gmticks;
+    wxInt64 gmticks;
 
     void Init(const wxDateTime::Tm& tm)
     {
@@ -184,7 +184,8 @@ static const Date testDates[] =
     {  8, wxDateTime::Feb,  2036, 00, 00, 00, 2464731.5, wxDateTime::Fri,        -1 },
     {  1, wxDateTime::Jan,  2037, 00, 00, 00, 2465059.5, wxDateTime::Thu,        -1 },
     {  1, wxDateTime::Jan,  2038, 00, 00, 00, 2465424.5, wxDateTime::Fri,        -1 },
-    { 21, wxDateTime::Jan,  2222, 00, 00, 00, 2532648.5, wxDateTime::Mon,        -1 },
+    {  1, wxDateTime::Jan,  2044, 00, 00, 00, 2467615.5, wxDateTime::Fri, 2335219200LL },
+    { 21, wxDateTime::Jan,  2222, 00, 00, 00, 2532648.5, wxDateTime::Mon, 7954070400LL },
     { 29, wxDateTime::May,  1976, 12, 00, 00, 2442928.0, wxDateTime::Sat, 202219200 },
     { 29, wxDateTime::Feb,  1976, 00, 00, 00, 2442837.5, wxDateTime::Sun, 194400000 },
     {  1, wxDateTime::Jan,  1900, 12, 00, 00, 2415021.0, wxDateTime::Mon,        -1 },
@@ -1072,7 +1073,7 @@ void DateTimeTestCase::TestTimeTicks()
 
         INFO("n=" << n);
 
-        time_t ticks = (dt.GetValue() / 1000).ToLong();
+        wxInt64 ticks = (dt.GetValue() / 1000).GetValue();
         CHECK( d.gmticks == ticks );
     }
 }
@@ -1111,6 +1112,12 @@ void DateTimeTestCase::TestParseRFC822()
             true
         },
 
+        {
+            "Tue, 12 Apr 2044 10:48:30 -0500",
+            { 12, wxDateTime::Apr, 2044, 15, 48, 30 },
+            true
+        },
+
         {
             "Sat, 18 Dec 1999 10:48:30 G", // military time zone
             { 18, wxDateTime::Dec, 1999, 17, 48, 30 },
@@ -1283,6 +1290,7 @@ void DateTimeTestCase::TestDateParse()
         { "31/03/06",    { 31, wxDateTime::Mar,    6 }, true, "" },
         { "31/03/2006",  { 31, wxDateTime::Mar, 2006 }, true, "" },
         { "Thu 20 Jun 2019", { 20, wxDateTime::Jun, 2019 }, true, "" },
+        { "Sun 20 Jun 2049", { 20, wxDateTime::Jun, 2049 }, true, "" },
         { "20 Jun 2019 Thu", { 20, wxDateTime::Jun, 2019 }, true, "" },
         { "Dec sixth 2017",  {  6, wxDateTime::Dec, 2017 }, true, "" },
 
@@ -1435,6 +1443,14 @@ void DateTimeTestCase::TestDateTimeParse()
             false
         },
 
+        {
+            "Sun 20 Jun 2049 07:40:00 PM",
+            { 20, wxDateTime::Jun, 2049, 19, 40,  0 },
+            true,
+            "",
+            false
+        },
+
         {
             "2010-01-04 14:30",
             {  4, wxDateTime::Jan, 2010, 14, 30,  0 },