Revert of Make dates default to the local timezone if none specified (https://codereview.chromium.…

src/dateparser-inl.h

Index: src/dateparser-inl.h
diff --git a/src/dateparser-inl.h b/src/dateparser-inl.h
index 5b3ac46025f05b09ae944c0cac42f95d7b6e3809..c1afb7d1b6e4352a3a547dc7bb9b65725b474cf6 100644
--- a/src/dateparser-inl.h
+++ b/src/dateparser-inl.h
@@ -24,9 +24,9 @@ bool DateParser::Parse(Vector<Char> str,
   DayComposer day;
 
   // Specification:
-  // Accept ES6 ISO 8601 date-time-strings or legacy dates compatible
+  // Accept ES5 ISO 8601 date-time-strings or legacy dates compatible
   // with Safari.
-  // ES6 ISO 8601 dates:
+  // ES5 ISO 8601 dates:
   //   [('-'|'+')yy]yyyy[-MM[-DD]][THH:mm[:ss[.sss]][Z|(+|-)hh:mm]]
   //   where yyyy is in the range 0000..9999 and
   //         +/-yyyyyy is in the range -999999..+999999 -
@@ -41,7 +41,8 @@ bool DateParser::Parse(Vector<Char> str,
   //         sss is in the range 000..999,
   //         hh is in the range 00..23,
   //         mm, ss, and sss default to 00 if missing, and
-  //         timezone defaults to local time if missing.
+  //         timezone defaults to Z if missing
+  //           (following Safari, ISO actually demands local time).
   //  Extensions:
   //   We also allow sss to have more or less than three digits (but at
   //   least one).
@@ -63,13 +64,15 @@ bool DateParser::Parse(Vector<Char> str,
   //  is allowed).
   // Intersection of the two:
   //  A string that matches both formats (e.g. 1970-01-01) will be
-  //  parsed as an ES6 date-time string.
-  //  After a valid "T" has been read while scanning an ES6 datetime string,
+  //  parsed as an ES5 date-time string - which means it will default
+  //  to UTC time-zone. That's unavoidable if following the ES5
+  //  specification.
+  //  After a valid "T" has been read while scanning an ES5 datetime string,
   //  the input can no longer be a valid legacy date, since the "T" is a
   //  garbage string after a number has been read.
 
-  // First try getting as far as possible with as ES6 Date Time String.
-  DateToken next_unhandled_token = ParseES6DateTime(&scanner, &day, &time, &tz);
+  // First try getting as far as possible with as ES5 Date Time String.
+  DateToken next_unhandled_token = ParseES5DateTime(&scanner, &day, &time, &tz);
   if (next_unhandled_token.IsInvalid()) return false;
   bool has_read_number = !day.IsEmpty();
   // If there's anything left, continue with the legacy parser.
@@ -217,10 +220,8 @@ bool DateParser::InputReader<Char>::SkipParentheses() {
 
 
 template <typename Char>
-DateParser::DateToken DateParser::ParseES6DateTime(
-    DateStringTokenizer<Char>* scanner,
-    DayComposer* day,
-    TimeComposer* time,
+DateParser::DateToken DateParser::ParseES5DateTime(
+    DateStringTokenizer<Char>* scanner, DayComposer* day, TimeComposer* time,
     TimeZoneComposer* tz) {
   DCHECK(day->IsEmpty());
   DCHECK(time->IsEmpty());
@@ -255,7 +256,7 @@ DateParser::DateToken DateParser::ParseES6DateTime(
   if (!scanner->Peek().IsKeywordType(TIME_SEPARATOR)) {
     if (!scanner->Peek().IsEndOfInput()) return scanner->Next();
   } else {
-    // ES6 Date Time String time part is present.
+    // ES5 Date Time String time part is present.
     scanner->Next();
     if (!scanner->Peek().IsFixedLengthNumber(2) ||
         !Between(scanner->Peek().number(), 0, 24)) {
@@ -321,7 +322,8 @@ DateParser::DateToken DateParser::ParseES6DateTime(
     }
     if (!scanner->Peek().IsEndOfInput()) return DateToken::Invalid();
   }
-  // Successfully parsed ES6 Date Time String.
+  // Successfully parsed ES5 Date Time String. Default to UTC if no TZ given.
+  if (tz->IsEmpty()) tz->Set(0);
   day->set_iso_date();
   return DateToken::EndOfInput();
 }