diff --git a/utils.go b/utils.go
index b0c6e9ca3..d6545f5be 100644
--- a/utils.go
+++ b/utils.go
@@ -277,15 +277,9 @@ func parseBinaryDateTime(num uint64, data []byte, loc *time.Location) (driver.Va
 }
 
 func appendDateTime(buf []byte, t time.Time) ([]byte, error) {
-	nsec := t.Nanosecond()
-	// to round under microsecond
-	if nsec%1000 >= 500 { // save half of time.Time.Add calls
-		t = t.Add(500 * time.Nanosecond)
-		nsec = t.Nanosecond()
-	}
 	year, month, day := t.Date()
 	hour, min, sec := t.Clock()
-	micro := nsec / 1000
+	nsec := t.Nanosecond()
 
 	if year < 1 || year > 9999 {
 		return buf, errors.New("year is not in the range [1, 9999]: " + strconv.Itoa(year)) // use errors.New instead of fmt.Errorf to avoid year escape to heap
@@ -293,14 +287,14 @@ func appendDateTime(buf []byte, t time.Time) ([]byte, error) {
 	year100 := year / 100
 	year1 := year % 100
 
-	var localBuf [26]byte // does not escape
+	var localBuf [len("2006-01-02T15:04:05.999999999")]byte // does not escape
 	localBuf[0], localBuf[1], localBuf[2], localBuf[3] = digits10[year100], digits01[year100], digits10[year1], digits01[year1]
 	localBuf[4] = '-'
 	localBuf[5], localBuf[6] = digits10[month], digits01[month]
 	localBuf[7] = '-'
 	localBuf[8], localBuf[9] = digits10[day], digits01[day]
 
-	if hour == 0 && min == 0 && sec == 0 && micro == 0 {
+	if hour == 0 && min == 0 && sec == 0 && nsec == 0 {
 		return append(buf, localBuf[:10]...), nil
 	}
 
@@ -311,18 +305,33 @@ func appendDateTime(buf []byte, t time.Time) ([]byte, error) {
 	localBuf[16] = ':'
 	localBuf[17], localBuf[18] = digits10[sec], digits01[sec]
 
-	if micro == 0 {
+	if nsec == 0 {
 		return append(buf, localBuf[:19]...), nil
 	}
-
-	micro10000 := micro / 10000
-	micro100 := (micro / 100) % 100
-	micro1 := micro % 100
+	nsec100000000 := nsec / 100000000
+	nsec1000000 := (nsec / 1000000) % 100
+	nsec10000 := (nsec / 10000) % 100
+	nsec100 := (nsec / 100) % 100
+	nsec1 := nsec % 100
 	localBuf[19] = '.'
-	localBuf[20], localBuf[21], localBuf[22], localBuf[23], localBuf[24], localBuf[25] =
-		digits10[micro10000], digits01[micro10000], digits10[micro100], digits01[micro100], digits10[micro1], digits01[micro1]
 
-	return append(buf, localBuf[:]...), nil
+	// milli second
+	localBuf[20], localBuf[21], localBuf[22] =
+		digits01[nsec100000000], digits10[nsec1000000], digits01[nsec1000000]
+	// micro second
+	localBuf[23], localBuf[24], localBuf[25] =
+		digits10[nsec10000], digits01[nsec10000], digits10[nsec100]
+	// nano second
+	localBuf[26], localBuf[27], localBuf[28] =
+		digits01[nsec100], digits10[nsec1], digits01[nsec1]
+
+	// trim trailing zeros
+	n := len(localBuf)
+	for n > 0 && localBuf[n-1] == '0' {
+		n--
+	}
+
+	return append(buf, localBuf[:n]...), nil
 }
 
 // zeroDateTime is used in formatBinaryDateTime to avoid an allocation
diff --git a/utils_test.go b/utils_test.go
index e3619e7a7..67b132d2b 100644
--- a/utils_test.go
+++ b/utils_test.go
@@ -299,40 +299,40 @@ func TestAppendDateTime(t *testing.T) {
 		str string
 	}{
 		{
-			t:   time.Date(2020, 05, 30, 0, 0, 0, 0, time.UTC),
-			str: "2020-05-30",
+			t:   time.Date(1234, 5, 6, 0, 0, 0, 0, time.UTC),
+			str: "1234-05-06",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 0, 0, 0, time.UTC),
-			str: "2020-05-30 22:00:00",
+			t:   time.Date(4567, 12, 31, 12, 0, 0, 0, time.UTC),
+			str: "4567-12-31 12:00:00",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 0, 0, time.UTC),
-			str: "2020-05-30 22:33:00",
+			t:   time.Date(2020, 5, 30, 12, 34, 0, 0, time.UTC),
+			str: "2020-05-30 12:34:00",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 44, 0, time.UTC),
-			str: "2020-05-30 22:33:44",
+			t:   time.Date(2020, 5, 30, 12, 34, 56, 0, time.UTC),
+			str: "2020-05-30 12:34:56",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 44, 550000000, time.UTC),
-			str: "2020-05-30 22:33:44.550000",
+			t:   time.Date(2020, 5, 30, 22, 33, 44, 123000000, time.UTC),
+			str: "2020-05-30 22:33:44.123",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 44, 550000499, time.UTC),
-			str: "2020-05-30 22:33:44.550000",
+			t:   time.Date(2020, 5, 30, 22, 33, 44, 123456000, time.UTC),
+			str: "2020-05-30 22:33:44.123456",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 44, 550000500, time.UTC),
-			str: "2020-05-30 22:33:44.550001",
+			t:   time.Date(2020, 5, 30, 22, 33, 44, 123456789, time.UTC),
+			str: "2020-05-30 22:33:44.123456789",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 44, 550000567, time.UTC),
-			str: "2020-05-30 22:33:44.550001",
+			t:   time.Date(9999, 12, 31, 23, 59, 59, 999999999, time.UTC),
+			str: "9999-12-31 23:59:59.999999999",
 		},
 		{
-			t:   time.Date(2020, 05, 30, 22, 33, 44, 999999567, time.UTC),
-			str: "2020-05-30 22:33:45",
+			t:   time.Date(1, 1, 1, 0, 0, 0, 0, time.UTC),
+			str: "0001-01-01",
 		},
 	}
 	for _, v := range tests {
@@ -340,7 +340,6 @@ func TestAppendDateTime(t *testing.T) {
 		buf, _ = appendDateTime(buf, v.t)
 		if str := string(buf); str != v.str {
 			t.Errorf("appendDateTime(%v), have: %s, want: %s", v.t, str, v.str)
-			return
 		}
 	}