fix(time): correct export data timestamp conversions (#586)

browser/safari/safari_test.go

@@ -5,6 +5,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -334,3 +335,32 @@ func TestExtractCategory(t *testing.T) {
 		assert.Empty(t, data.CreditCards)
 	})
 }
+
+// Anchor: 2024-01-15T10:30:00Z, in seconds past the Core Data epoch (2001-01-01Z).
+const anchorCoreDataSeconds = 1705314600 - 978307200
+
+func TestCoredataTimestamp_AnchorDate(t *testing.T) {
+	got := coredataTimestamp(float64(anchorCoreDataSeconds))
+	want := time.Date(2024, 1, 15, 10, 30, 0, 0, time.UTC)
+	assert.Equal(t, want, got)
+}
+
+func TestCoredataTimestamp_EpochZero(t *testing.T) {
+	assert.True(t, coredataTimestamp(0).IsZero())
+}
+
+func TestCoredataTimestamp_NegativeReturnsZeroTime(t *testing.T) {
+	assert.True(t, coredataTimestamp(-1).IsZero())
+}
+
+func TestCoredataTimestamp_FractionalSecondsPreserved(t *testing.T) {
+	got := coredataTimestamp(float64(anchorCoreDataSeconds) + 0.5)
+	assert.Equal(t, 500*int64(time.Millisecond), int64(got.Nanosecond()))
+}
+
+func TestCoredataTimestamp_AlwaysUTC(t *testing.T) {
+	// assert.Same: pointer equality reliably catches any regression that
+	// leaks time.Local, independent of the runner's configured TZ.
+	got := coredataTimestamp(float64(anchorCoreDataSeconds))
+	assert.Same(t, time.UTC, got.Location())
+}