crypto/tls: update generate_cert.go for new time package

Fixes #2635.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5512043

generate_cert.go

@@ -31,7 +31,7 @@ func main() {
 		return
 	}
 
-	now := time.Seconds()
+	now := time.Now()
 
 	template := x509.Certificate{
 		SerialNumber: new(big.Int).SetInt64(0),
@@ -39,8 +39,8 @@ func main() {
 			CommonName:   *hostName,
 			Organization: []string{"Acme Co"},
 		},
-		NotBefore: time.SecondsToUTC(now - 300),
-		NotAfter:  time.SecondsToUTC(now + 60*60*24*365), // valid for 1 year.
+		NotBefore: now.Add(-5 * time.Minute).UTC(),
+		NotAfter:  now.AddDate(1, 0, 0).UTC(), // valid for 1 year.
 
 		SubjectKeyId: []byte{1, 2, 3, 4},
 		KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,