diff --git a/pkg/action/package.go b/pkg/action/package.go
index ebacd4da0..d3e8d1a52 100644
--- a/pkg/action/package.go
+++ b/pkg/action/package.go
@@ -267,8 +267,11 @@ func openPassphraseFile(passphraseFile string, stdin *os.File) (*os.File, error)
 }
 
 // stampModTimes recursively sets all file modification times in a chart to t.
+// t is normalized to UTC and truncated to whole seconds before use because tar
+// headers have second-level granularity and timezone-independent storage.
 // This is used to produce reproducible archives when SourceDateEpoch is set.
 func stampModTimes(c *chart.Chart, t time.Time) {
+	t = t.UTC().Truncate(time.Second)
 	c.ModTime = t
 	c.SchemaModTime = t
 	for _, f := range c.Raw {
diff --git a/pkg/action/package_test.go b/pkg/action/package_test.go
index 2c8749a2c..89f6385b3 100644
--- a/pkg/action/package_test.go
+++ b/pkg/action/package_test.go
@@ -177,7 +177,8 @@ func TestRun(t *testing.T) {
 
 func TestRunWithSourceDateEpoch(t *testing.T) {
 	chartPath := "testdata/charts/chart-with-schema"
-	epoch := time.Unix(1700000000, 0)
+	// Use UTC so the comparison with tar header ModTime (always UTC) is straightforward.
+	epoch := time.Unix(1700000000, 0).UTC()
 
 	client := NewPackage()
 	client.SourceDateEpoch = &epoch
@@ -186,15 +187,18 @@ func TestRunWithSourceDateEpoch(t *testing.T) {
 	require.NoError(t, err)
 	t.Cleanup(func() { os.Remove(filename) })
 
-	// All tar entry ModTimes must equal the epoch.
 	f, err := os.Open(filename)
 	require.NoError(t, err)
 	defer f.Close()
 
+	// Check gzip header ModTime: helm leaves it at zero (deterministic by design).
 	gr, err := gzip.NewReader(f)
 	require.NoError(t, err)
+	require.True(t, gr.Header.ModTime.IsZero(), "gzip header ModTime should be zero")
 	defer gr.Close()
 
+	// All tar entry ModTimes must represent the same instant as epoch.
+	// tar.Reader returns ModTime in local timezone, so use Equal() not require.Equal.
 	tr := tar.NewReader(gr)
 	for {
 		hdr, err := tr.Next()
@@ -202,7 +206,7 @@ func TestRunWithSourceDateEpoch(t *testing.T) {
 			break
 		}
 		require.NoError(t, err)
-		require.Equal(t, epoch, hdr.ModTime, "expected epoch ModTime for entry %s", hdr.Name)
+		require.True(t, epoch.Equal(hdr.ModTime), "entry %s: got ModTime %v, want %v", hdr.Name, hdr.ModTime, epoch)
 	}
 }