# HG changeset patch
# User André Bargull <andre.bargull@gmail.com>
# Date 1510140221 28800
#      Wed Nov 08 03:23:41 2017 -0800
# Node ID 8bf5e7460a7c5ba3430b501d1659c469a862a929
# Parent  60fd4a5b01ec70ded9ddfd560fd5be191b1c74b9
Bug 1415202: Always use the equivalent year to determine the time zone offset and name. r=Waldo

diff --git a/js/src/jsdate.cpp b/js/src/jsdate.cpp
--- a/js/src/jsdate.cpp
+++ b/js/src/jsdate.cpp
@@ -2348,22 +2348,26 @@ static PRMJTime ToPRMJTime(double localT
   prtm.tm_isdst = (DaylightSavingTA(utcTime) != 0);
 
   return prtm;
 }
 
 static size_t FormatTime(char* buf, int buflen, const char* fmt, double utcTime,
                          double localTime) {
   PRMJTime prtm = ToPRMJTime(localTime, utcTime);
-  int eqivalentYear = IsRepresentableAsTime32(utcTime)
+
+  // If an equivalent year was used to compute the date/time components, use
+  // the same equivalent year to determine the time zone name and offset in
+  // PRMJ_FormatTime(...).
+  int timeZoneYear = IsRepresentableAsTime32(utcTime)
                           ? prtm.tm_year
                           : EquivalentYearForDST(prtm.tm_year);
   int offsetInSeconds = (int)floor((localTime - utcTime) / msPerSecond);
 
-  return PRMJ_FormatTime(buf, buflen, fmt, &prtm, eqivalentYear,
+  return PRMJ_FormatTime(buf, buflen, fmt, &prtm, timeZoneYear,
                          offsetInSeconds);
 }
 
 enum class FormatSpec { DateTime, Date, Time };
 
 static bool FormatDate(JSContext* cx, double utcTime, FormatSpec format,
                        MutableHandleValue rval) {
   JSString* str;
diff --git a/js/src/vm/Time.cpp b/js/src/vm/Time.cpp
--- a/js/src/vm/Time.cpp
+++ b/js/src/vm/Time.cpp
@@ -242,17 +242,17 @@ static void PRMJ_InvalidParameterHandler
                                          const wchar_t* file, unsigned int line,
                                          uintptr_t pReserved) {
   /* empty */
 }
 #endif
 
 /* Format a time value into a buffer. Same semantics as strftime() */
 size_t PRMJ_FormatTime(char* buf, int buflen, const char* fmt,
-                       const PRMJTime* prtm, int equivalentYear,
+                       const PRMJTime* prtm, int timeZoneYear,
                        int offsetInSeconds) {
   size_t result = 0;
 #if defined(XP_UNIX) || defined(XP_WIN)
   struct tm a;
 #ifdef XP_WIN
   _invalid_parameter_handler oldHandler;
 #ifndef __MINGW32__
   int oldReportMode;
@@ -275,39 +275,33 @@ size_t PRMJ_FormatTime(char* buf, int bu
    */
 #if defined(HAVE_LOCALTIME_R) && defined(HAVE_TM_ZONE_TM_GMTOFF)
   char emptyTimeZoneId[] = "";
   {
     /*
      * Fill out |td| to the time represented by |prtm|, leaving the
      * timezone fields zeroed out. localtime_r will then fill in the
      * timezone fields for that local time according to the system's
-     * timezone parameters.
+     * timezone parameters. Use |timeZoneYear| for the year to ensure the
+     * time zone name matches the time zone offset used by the caller.
      */
     struct tm td;
     memset(&td, 0, sizeof(td));
     td.tm_sec = prtm->tm_sec;
     td.tm_min = prtm->tm_min;
     td.tm_hour = prtm->tm_hour;
     td.tm_mday = prtm->tm_mday;
     td.tm_mon = prtm->tm_mon;
     td.tm_wday = prtm->tm_wday;
-    td.tm_year = prtm->tm_year - 1900;
+    td.tm_year = timeZoneYear - 1900;
     td.tm_yday = prtm->tm_yday;
     td.tm_isdst = prtm->tm_isdst;
 
     time_t t = mktime(&td);
 
-    // If |prtm| cannot be represented in |time_t| the year is probably
-    // out of range, try again with the DST equivalent year.
-    if (t == static_cast<time_t>(-1)) {
-      td.tm_year = equivalentYear - 1900;
-      t = mktime(&td);
-    }
-
     // If either mktime or localtime_r failed, fill in the fallback time
     // zone offset |offsetInSeconds| and set the time zone identifier to
     // the empty string.
     if (t != static_cast<time_t>(-1) && localtime_r(&t, &td)) {
       a.tm_gmtoff = td.tm_gmtoff;
       a.tm_zone = td.tm_zone;
     } else {
       a.tm_gmtoff = offsetInSeconds;
diff --git a/js/src/vm/Time.h b/js/src/vm/Time.h
--- a/js/src/vm/Time.h
+++ b/js/src/vm/Time.h
@@ -44,17 +44,17 @@ inline void PRMJ_NowInit() {}
 #ifdef XP_WIN
 extern void PRMJ_NowShutdown();
 #else
 inline void PRMJ_NowShutdown() {}
 #endif
 
 /* Format a time value into a buffer. Same semantics as strftime() */
 extern size_t PRMJ_FormatTime(char* buf, int buflen, const char* fmt,
-                              const PRMJTime* tm, int equivalentYear,
+                              const PRMJTime* tm, int timeZoneYear,
                               int offsetInSeconds);
 
 /**
  * Requesting the number of cycles from the CPU.
  *
  * `rdtsc`, or Read TimeStamp Cycle, is an instruction provided by
  * x86-compatible CPUs that lets processes request the number of
  * cycles spent by the CPU executing instructions since the CPU was