time.RFC822: make the string standard-compliant

For mysterious reasons, the existing string was just wrong: it was missing a colon.
There is no apparent reason for this discrepancy.

This should be safe to fix because existing uses would not be RFC822-compliant;
people cannot be depending on it to generate correct mail headers.

Fixes #3444.

R=golang-dev, dsymonds, iant, rsc
CC=golang-dev
https://golang.org/cl/5969072

src/pkg/time/format.go

@@ -41,8 +41,8 @@ const (
 	ANSIC       = "Mon Jan _2 15:04:05 2006"
 	UnixDate    = "Mon Jan _2 15:04:05 MST 2006"
 	RubyDate    = "Mon Jan 02 15:04:05 -0700 2006"
-	RFC822      = "02 Jan 06 1504 MST"
-	RFC822Z     = "02 Jan 06 1504 -0700" // RFC822 with numeric zone
+	RFC822      = "02 Jan 06 15:04 MST"
+	RFC822Z     = "02 Jan 06 15:04 -0700" // RFC822 with numeric zone
 	RFC850      = "Monday, 02-Jan-06 15:04:05 MST"
 	RFC1123     = "Mon, 02 Jan 2006 15:04:05 MST"
 	RFC1123Z    = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone

src/pkg/time/time_test.go

@@ -223,7 +223,7 @@ var formatTests = []FormatTest{
 	{"ANSIC", ANSIC, "Wed Feb  4 21:00:57 2009"},
 	{"UnixDate", UnixDate, "Wed Feb  4 21:00:57 PST 2009"},
 	{"RubyDate", RubyDate, "Wed Feb 04 21:00:57 -0800 2009"},
-	{"RFC822", RFC822, "04 Feb 09 2100 PST"},
+	{"RFC822", RFC822, "04 Feb 09 21:00 PST"},
 	{"RFC850", RFC850, "Wednesday, 04-Feb-09 21:00:57 PST"},
 	{"RFC1123", RFC1123, "Wed, 04 Feb 2009 21:00:57 PST"},
 	{"RFC1123Z", RFC1123Z, "Wed, 04 Feb 2009 21:00:57 -0800"},