fix +0000 time zones.

Fixes #527.

R=rsc
CC=golang-dev
https://golang.org/cl/186159

src/pkg/time/format.go

@@ -326,9 +326,9 @@ func Parse(alayout, avalue string) (*Time, os.Error) {
 		prevLayout := layout
 		layout = layout[i:]
 		// Ugly time zone handling.
-		if reference == "Z" || reference == "z" {
+		if reference == "Z" {
 			// Special case for ISO8601 time zone: "Z" or "-0800"
-			if reference == "Z" && value[0] == 'Z' {
+			if value[0] == 'Z' {
 				i = 1
 			} else if len(value) >= 5 {
 				i = 5
@@ -338,11 +338,19 @@ func Parse(alayout, avalue string) (*Time, os.Error) {
 		} else {
 			c = value[0]
 			if charType(c) != pieceType {
-				// could be a minus sign introducing a negative year
+				// Ugly management of signs.  Reference and data might differ.
+				// 1. Could be a minus sign introducing a negative year.
 				if c == '-' && pieceType != minus {
 					value = value[1:]
-					sign = "-"
 					layout = prevLayout // don't consume reference item
+					sign = "-"
+					continue
+				}
+				// 2. Could be a plus sign for a +0100 time zone, represented by -0700 in the standard.
+				if c == '+' && pieceType == minus {
+					value = value[1:]
+					layout = prevLayout[1:] // absorb sign in both value and layout
+					sign = "+"
 					continue
 				}
 				return nil, &ParseError{Layout: alayout, Value: avalue, Message: formatErr + alayout}

src/pkg/time/time_test.go

@@ -186,6 +186,26 @@ func TestParse(t *testing.T) {
 	}
 }
 
+var rubyTests = []ParseTest{
+	ParseTest{"RubyDate", RubyDate, "Thu Feb 04 21:00:57 -0800 2010", true, true, 1},
+	// Ignore the time zone in the test. If it parses, it'll be OK.
+	ParseTest{"RubyDate", RubyDate, "Thu Feb 04 21:00:57 -0000 2010", false, true, 1},
+	ParseTest{"RubyDate", RubyDate, "Thu Feb 04 21:00:57 +0000 2010", false, true, 1},
+	ParseTest{"RubyDate", RubyDate, "Thu Feb 04 21:00:57 +1130 2010", false, true, 1},
+}
+
+// Problematic time zone format needs special tests.
+func TestRubyParse(t *testing.T) {
+	for _, test := range rubyTests {
+		time, err := Parse(test.format, test.value)
+		if err != nil {
+			t.Errorf("%s error: %v", test.name, err)
+		} else {
+			checkTime(time, &test, t)
+		}
+	}
+}
+
 func checkTime(time *Time, test *ParseTest, t *testing.T) {
 	// The time should be Thu Feb  4 21:00:57 PST 2010
 	if test.yearSign*time.Year != 2010 {