[premature PR publish]

src/time/format.go

@@ -973,6 +973,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 	rangeErrString := "" // set if a value is out of range
 	amSet := false       // do we need to subtract 12 from the hour for midnight?
 	pmSet := false       // do we need to add 12 to the hour?
+	secsSet := false     // are seconds explictly set?
 
 	// Time being constructed.
 	var (
@@ -1159,12 +1160,14 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 					break
 				}
 				sign, hour, min, seconds, value = value[0:1], value[1:3], value[4:6], value[7:9], value[9:]
+				secsSet = true
 			} else if std == stdISO8601SecondsTZ || std == stdNumSecondsTz {
 				if len(value) < 7 {
 					err = errBad
 					break
 				}
 				sign, hour, min, seconds, value = value[0:1], value[1:3], value[3:5], value[5:7], value[7:]
+				secsSet = true
 			} else {
 				if len(value) < 5 {
 					err = errBad
@@ -1297,6 +1300,15 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 		// Look for local zone with the given offset.
 		// If that zone was in effect at the given time, use it.
 		name, offset, _, _, _ := local.lookup(t.unixSec())
+
+		if !secsSet {
+			if diff := offset - zoneOffset; -60 < diff && diff < 60 {
+				// The difference of local offset and the zone offset is mere seconds and seconds weren't explictly set.
+				t.addSec(-int64(diff))
+				zoneOffset += diff
+			}
+		}
+
 		if offset == zoneOffset && (zoneName == "" || name == zoneName) {
 			t.setLoc(local)
 			return t, nil

src/time/format_test.go

@@ -893,3 +893,35 @@ func TestParseFractionalSecondsLongerThanNineDigits(t *testing.T) {
 		}
 	}
 }
+
+// Issue 53919
+func TestParseInLocationSecondsAdjusted(t *testing.T) {
+	t.Parallel()
+
+	zName := "Asia/Shanghai"
+
+	z, err := LoadLocation(zName)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+		return
+	}
+
+	ts := Date(1900, 1, 1, 0, 0, 0, 0, z)
+	s := ts.Format(RFC3339Nano)
+
+	ts, err = ParseInLocation(RFC3339, s, z)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+		return
+	}
+
+	if got := ts.Location().String(); zName != got {
+		t.Errorf("ParseInLocation returns wrong location; got %q, want %q", got, zName)
+
+		ts = ts.In(z)
+	}
+
+	if got := ts.Format(RFC3339Nano); s != got {
+		t.Errorf("Seconds were not adjusted; got %q, want %q", got, s)
+	}
+}