time: do not segment time strings by character class.

instead use pure substring matching to find template values.

this makes stdZulu unnecessary and allows formats
like "20060102 030405" (used in some internet protocols).

this makes Parse not handle years < 0000 or > 9999 anymore.
that seems like an okay price to pay, trading hypothetical
functionality for real functionality.

also changed the comments on the Time struct to use the
same reference date as the format and parse routines.

R=r
CC=golang-dev
https://golang.org/cl/833045

src/pkg/time/time.go

@@ -43,12 +43,12 @@ const (
 
 // Time is the struct representing a parsed time value.
 type Time struct {
-	Year                 int64 // 2008 is 2008
-	Month, Day           int   // Sep-17 is 9, 17
-	Hour, Minute, Second int   // 10:43:12 is 10, 43, 12
-	Weekday              int   // Sunday, Monday, ...
-	ZoneOffset           int   // seconds east of UTC
-	Zone                 string
+	Year                 int64  // 2006 is 2006
+	Month, Day           int    // Jan-2 is 1, 2
+	Hour, Minute, Second int    // 15:04:05 is 15, 4, 5.
+	Weekday              int    // Sunday, Monday, ...
+	ZoneOffset           int    // seconds east of UTC, e.g. -7*60 for -0700
+	Zone                 string // e.g., "MST"
 }
 
 var nonleapyear = []int{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}

src/pkg/time/time_test.go

@@ -169,8 +169,6 @@ var parseTests = []ParseTest{
 	ParseTest{"RFC850", RFC850, "Thursday, 04-Feb-10 21:00:57 PST", true, true, 1},
 	ParseTest{"RFC1123", RFC1123, "Thu, 04 Feb 2010 21:00:57 PST", true, true, 1},
 	ParseTest{"ISO8601", ISO8601, "2010-02-04T21:00:57-0800", true, false, 1},
-	// Negative year
-	ParseTest{"ANSIC", ANSIC, "Thu Feb  4 21:00:57 -2010", false, true, -1},
 	// Amount of white space should not matter.
 	ParseTest{"ANSIC", ANSIC, "Thu Feb 4 21:00:57 2010", false, true, 1},
 	ParseTest{"ANSIC", ANSIC, "Thu      Feb     4     21:00:57     2010", false, true, 1},
@@ -239,6 +237,10 @@ func TestFormatAndParse(t *testing.T) {
 	const fmt = "Mon MST " + ISO8601 // all fields
 	f := func(sec int64) bool {
 		t1 := SecondsToLocalTime(sec)
+		if t1.Year < 1000 || t1.Year > 9999 {
+			// not required to work
+			return true
+		}
 		t2, err := Parse(fmt, t1.Format(fmt))
 		if err != nil {
 			t.Errorf("error: %s", err)
@@ -270,7 +272,7 @@ type ParseErrorTest struct {
 
 var parseErrorTests = []ParseErrorTest{
 	ParseErrorTest{ANSIC, "Feb  4 21:00:60 2010", "parse"}, // cannot parse Feb as Mon
-	ParseErrorTest{ANSIC, "Thu Feb  4 21:00:57 @2010", "format"},
+	ParseErrorTest{ANSIC, "Thu Feb  4 21:00:57 @2010", "parse"},
 	ParseErrorTest{ANSIC, "Thu Feb  4 21:00:60 2010", "second out of range"},
 	ParseErrorTest{ANSIC, "Thu Feb  4 21:61:57 2010", "minute out of range"},
 	ParseErrorTest{ANSIC, "Thu Feb  4 24:00:60 2010", "hour out of range"},