pkg/time: use UTC time zone for Unix and Parse

Change-Id: Ia38856c40bfca70620c7783d41ea3936a020b745
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2726
Reviewed-by: Marcel van Lohuizen <[email protected]>

Author: mpvl

pkg/time/time.go

@@ -189,7 +189,7 @@ func Parse(layout, value string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return t.Format(time.RFC3339Nano), nil
+	return t.UTC().Format(time.RFC3339Nano), nil
 }
 
 // Unix returns the local Time corresponding to the given Unix time,
@@ -199,5 +199,5 @@ func Parse(layout, value string) (string, error) {
 // value is 1<<63-1 (the largest int64 value).
 func Unix(sec int64, nsec int64) string {
 	t := time.Unix(sec, nsec)
-	return t.Format(time.RFC3339Nano)
+	return t.UTC().Format(time.RFC3339Nano)
 }

pkg/time/time_test.go

@@ -102,8 +102,8 @@ func TestUnix(t *testing.T) {
 		nano int64
 		want string
 	}{
-		{0, 0, "1970-01-01T01:00:00+01:00"},
-		{1500000000, 123456, "2017-07-14T04:40:00.000123456+02:00"},
+		{0, 0, "1970-01-01T00:00:00Z"},
+		{1500000000, 123456, "2017-07-14T02:40:00.000123456Z"},
 	}
 
 	for _, tc := range valid {