diff --git a/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/SmithyGoDependency.java b/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/SmithyGoDependency.java
index e0e546c59..f28ef2980 100644
--- a/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/SmithyGoDependency.java
+++ b/codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/SmithyGoDependency.java
@@ -118,7 +118,7 @@ private static GoDependency relativePackage(
     private static final class Versions {
         private static final String GO_STDLIB = "1.15";
         private static final String GO_CMP = "v0.5.4";
-        private static final String SMITHY_GO = "v0.0.0-20210113172615-49588e1e8525";
+        private static final String SMITHY_GO = "v0.5.1-0.20210115041537-09631dea532e";
         private static final String GO_JMESPATH = "v0.4.0";
     }
 }
diff --git a/time/time.go b/time/time.go
index 0a3fbe48c..35a387031 100644
--- a/time/time.go
+++ b/time/time.go
@@ -2,6 +2,7 @@ package time
 
 import (
 	"context"
+	"math/big"
 	"time"
 )
 
@@ -13,6 +14,8 @@ const (
 	httpDateFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
 )
 
+var millisecondFloat = big.NewFloat(1e3)
+
 // FormatDateTime format value as a date-time (RFC3339 section 5.6)
 //
 // Example: 1985-04-12T23:20:50.52Z
@@ -43,16 +46,20 @@ func ParseHTTPDate(value string) (time.Time, error) {
 
 // FormatEpochSeconds returns value as a Unix time in seconds with with decimal precision
 //
-// Example: 1515531081.1234
+// Example: 1515531081.123
 func FormatEpochSeconds(value time.Time) float64 {
-	return float64(value.UnixNano()) / float64(time.Second)
+	ms := value.UnixNano() / int64(time.Millisecond)
+	return float64(ms)/1e3
 }
 
 // ParseEpochSeconds returns value as a Unix time in seconds with with decimal precision
 //
-// Example: 1515531081.1234
+// Example: 1515531081.123
 func ParseEpochSeconds(value float64) time.Time {
-	return time.Unix(0, int64(value*float64(time.Second))).UTC()
+	f := big.NewFloat(value)
+	f = f.Mul(f, millisecondFloat)
+	i, _ := f.Int64()
+	return time.Unix(0, i*1e6).UTC()
 }
 
 // SleepWithContext will wait for the timer duration to expire, or the context
diff --git a/time/time_test.go b/time/time_test.go
index 533ef0f6d..4b3b698d6 100644
--- a/time/time_test.go
+++ b/time/time_test.go
@@ -1,6 +1,8 @@
 package time
 
 import (
+	"math"
+	"strconv"
 	"testing"
 	"time"
 )
@@ -42,16 +44,50 @@ func TestHTTPDate(t *testing.T) {
 }
 
 func TestEpochSeconds(t *testing.T) {
-	refTime := time.Date(2018, 1, 9, 20, 51, 21, 123399936, time.UTC)
-
-	epochSeconds := FormatEpochSeconds(refTime)
-	if e, a := 1515531081.1234, epochSeconds; e != a {
-		t.Errorf("expected %v, got %v", e, a)
+	cases := []struct {
+		reference    time.Time
+		expectedUnix float64
+		expectedTime time.Time
+	}{
+		{
+			reference:    time.Date(2018, 1, 9, 20, 51, 21, 123399936, time.UTC),
+			expectedUnix: 1515531081.123,
+			expectedTime: time.Date(2018, 1, 9, 20, 51, 21, 1.23e8, time.UTC),
+		},
+		{
+			reference:    time.Date(2018, 1, 9, 20, 51, 21, 1e8, time.UTC),
+			expectedUnix: 1515531081.1,
+			expectedTime: time.Date(2018, 1, 9, 20, 51, 21, 1e8, time.UTC),
+		},
+		{
+			reference:    time.Date(2018, 1, 9, 20, 51, 21, 123567891, time.UTC),
+			expectedUnix: 1515531081.123,
+			expectedTime: time.Date(2018, 1, 9, 20, 51, 21, 1.23e8, time.UTC),
+		},
+		{
+			reference: time.Unix(0, math.MaxInt64).UTC(),
+			expectedUnix: 9223372036.854,
+			expectedTime: time.Date(2262, 04, 11, 23, 47, 16, 8.54e8, time.UTC),
+		},
 	}
 
-	parseTime := ParseEpochSeconds(epochSeconds)
+	for i, tt := range cases {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			epochSeconds := FormatEpochSeconds(tt.reference)
+			if e, a := tt.expectedUnix, epochSeconds; e != a {
+				t.Errorf("expected %v, got %v", e, a)
+			}
 
-	if e, a := refTime, parseTime; !e.Equal(a) {
+			parseTime := ParseEpochSeconds(epochSeconds)
+
+			if e, a := tt.expectedTime, parseTime; !e.Equal(a) {
+				t.Errorf("expected %v, got %v", e, a)
+			}
+		})
+	}
+
+	// Check an additional edge that higher precision values are truncated to milliseconds
+	if e, a := time.Date(2018, 1, 9, 20, 51, 21, 1.23e8, time.UTC), ParseEpochSeconds(1515531081.12356); !e.Equal(a) {
 		t.Errorf("expected %v, got %v", e, a)
 	}
 }