统一时间格式和时区

backend/internal/pkg/timeutil/timeutil.go

@@ -0,0 +1,31 @@
+package timeutil
+
+import "time"
+
+const (
+	APITimeLayout = "2006-01-02T15:04:05-07:00"
+	OrderNoLayout = "20060102150405"
+)
+
+var businessLocation = time.FixedZone("CST", 8*60*60)
+
+func Location() *time.Location {
+	return businessLocation
+}
+
+func Now() time.Time {
+	return time.Now().In(businessLocation)
+}
+
+func FormatAPITime(value time.Time) string {
+	if value.IsZero() {
+		return ""
+	}
+	return value.In(businessLocation).Truncate(time.Second).Format(APITimeLayout)
+}
+
+func StartOfDay(value time.Time) time.Time {
+	local := value.In(businessLocation)
+	year, month, day := local.Date()
+	return time.Date(year, month, day, 0, 0, 0, 0, businessLocation)
+}

backend/internal/pkg/timeutil/timeutil_test.go

@@ -0,0 +1,21 @@
+package timeutil
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFormatAPITimeUsesBusinessTimezone(t *testing.T) {
+	value := time.Date(2026, 7, 30, 9, 53, 58, 147355000, time.UTC)
+	if got := FormatAPITime(value); got != "2026-07-30T17:53:58+08:00" {
+		t.Fatalf("unexpected api time: %s", got)
+	}
+}
+
+func TestStartOfDayUsesBusinessTimezone(t *testing.T) {
+	value := time.Date(2026, 7, 30, 18, 30, 0, 0, time.UTC)
+	got := StartOfDay(value)
+	if got.Format(APITimeLayout) != "2026-07-31T00:00:00+08:00" {
+		t.Fatalf("unexpected day start: %s", got.Format(APITimeLayout))
+	}
+}