diff --git a/backend/pkg/billingsync/sync.go b/backend/pkg/billingsync/sync.go
index 72bc283..12f79bb 100644
--- a/backend/pkg/billingsync/sync.go
+++ b/backend/pkg/billingsync/sync.go
@@ -23,7 +23,16 @@ type Result struct {
 
 // Yesterday 昨日日期 YYYY-MM-DD
 func Yesterday() string {
-	return time.Now().AddDate(0, 0, -1).Format("2006-01-02")
+	return billingYesterdayAt(time.Now())
+}
+
+// billingYesterdayAt 按平台业务时区计算昨日，避免服务器 UTC 时区造成日期偏差。 // Logan.Li
+func billingYesterdayAt(now time.Time) string {
+	location, err := time.LoadLocation("Asia/Shanghai")
+	if err != nil {
+		location = time.FixedZone("CST", 8*60*60)
+	}
+	return now.In(location).AddDate(0, 0, -1).Format("2006-01-02")
 }
 
 // SyncDate 同步指定日期账单（全部或单个活跃云账号）
diff --git a/backend/pkg/billingsync/sync_test.go b/backend/pkg/billingsync/sync_test.go
new file mode 100644
index 0000000..6da20ab
--- /dev/null
+++ b/backend/pkg/billingsync/sync_test.go
@@ -0,0 +1,14 @@
+package billingsync
+
+import (
+	"testing"
+	"time"
+)
+
+// TestBillingYesterdayAt 验证 UTC 服务器按中国业务时区计算昨日。 // Logan.Li
+func TestBillingYesterdayAt(t *testing.T) {
+	now := time.Date(2026, 7, 28, 21, 30, 0, 0, time.UTC)
+	if got := billingYesterdayAt(now); got != "2026-07-28" {
+		t.Fatalf("昨日日期错误: got=%s want=2026-07-28", got)
+	}
+}