diff --git a/time.go b/time.go
index dd334163..00ce754c 100644
--- a/time.go
+++ b/time.go
@@ -15,7 +15,7 @@ func (m RelaxedTime) MarshalText() ([]byte, error) {
 }
 
 func (m RelaxedTime) String() string {
-	return time.Time(m).UTC().Format(timeFormat)
+	return time.Time(m).Round(time.Millisecond).UTC().Format(timeFormat)
 }
 
 func (m *RelaxedTime) UnmarshalText(text []byte) error {
@@ -25,18 +25,21 @@ func (m *RelaxedTime) UnmarshalText(text []byte) error {
 	}
 	t, err1 := time.Parse(time.RFC3339, string(text))
 	if err1 == nil {
+		t = t.Round(time.Millisecond)
 		*m = RelaxedTime(t)
 		return nil
 	}
 
 	t, err2 := time.Parse(time.RFC3339Nano, string(text))
 	if err2 == nil {
+		t = t.Round(time.Millisecond)
 		*m = RelaxedTime(t)
 		return nil
 	}
 
 	t, err2 = time.Parse("2006-01-02T15:04:05.999999999", string(text))
 	if err2 == nil {
+		t = t.Round(time.Millisecond)
 		*m = RelaxedTime(t)
 		return nil
 	}
diff --git a/time_test.go b/time_test.go
new file mode 100644
index 00000000..c8f3277d
--- /dev/null
+++ b/time_test.go
@@ -0,0 +1,57 @@
+package saml
+
+import (
+	"time"
+
+	. "gopkg.in/check.v1"
+)
+
+var _ = Suite(&TimeTest{})
+
+type TimeTest struct {
+}
+
+func (test *TimeTest) TestFormat(c *C) {
+	t := time.Date(1981, 02, 03, 14, 15, 16, 17, time.UTC)
+	c.Assert(RelaxedTime(t).String(), Equals, "1981-02-03T14:15:16Z")
+
+	buf, err := RelaxedTime(t).MarshalText()
+	c.Assert(err, IsNil)
+	c.Assert(string(buf), Equals, "1981-02-03T14:15:16Z")
+
+	loc, err := time.LoadLocation("America/New_York")
+	c.Assert(err, IsNil)
+	t = time.Date(1981, 02, 03, 9, 15, 16, 17, loc)
+
+	c.Assert(RelaxedTime(t).String(), Equals, "1981-02-03T14:15:16Z")
+	buf, err = RelaxedTime(t).MarshalText()
+	c.Assert(err, IsNil)
+	c.Assert(string(buf), Equals, "1981-02-03T14:15:16Z")
+}
+
+func (test *TimeTest) TestParse(c *C) {
+	{
+		var t RelaxedTime
+		err := t.UnmarshalText([]byte("1981-02-03T14:15:16Z"))
+		c.Assert(err, IsNil)
+		c.Assert(t, DeepEquals, RelaxedTime(time.Date(1981, 02, 03, 14, 15, 16, 0, time.UTC)))
+	}
+
+	{
+		var t RelaxedTime
+		err := t.UnmarshalText([]byte("1981-02-03T14:15:16.178901234Z"))
+		c.Assert(err, IsNil)
+		c.Assert(t, DeepEquals, RelaxedTime(time.Date(1981, 02, 03, 14, 15, 16, 179000000, time.UTC)))
+	}
+	{
+		var t RelaxedTime
+		err := t.UnmarshalText([]byte("1981-02-03T14:15:16.1717Z"))
+		c.Assert(err, IsNil)
+		c.Assert(t, DeepEquals, RelaxedTime(time.Date(1981, 02, 03, 14, 15, 16, 172000000, time.UTC)))
+	}
+	{
+		var t RelaxedTime
+		err := t.UnmarshalText([]byte("1981-02-03T14:15:16Z04:00"))
+		c.Assert(err, ErrorMatches, "parsing time \"1981-02-03T14:15:16Z04:00\": extra text: 04:00")
+	}
+}