Fix commission export dates appearing a day early

apps/web/app/(ee)/api/commissions/export/route.ts

@@ -51,6 +51,7 @@ export const GET = withWorkspace(
     const formattedCommissions = formatCommissionsForExport(
       commissions,
       columns,
+      filters.timezone,
     );
 
     return new Response(convertToCSV(formattedCommissions), {

apps/web/app/(ee)/api/cron/export/commissions/route.ts

@@ -75,7 +75,9 @@ export async function POST(req: Request) {
     for await (const { commissions } of fetchCommissionsBatch(
       commissionsFilters,
     )) {
-      allCommissions.push(...formatCommissionsForExport(commissions, columns));
+      allCommissions.push(
+        ...formatCommissionsForExport(commissions, columns, filters.timezone),
+      );
     }
 
     const csvData = convertToCSV(allCommissions);

apps/web/lib/api/commissions/format-commissions-for-export.ts

@@ -1,5 +1,8 @@
+import { sanitizeTimezone } from "@/lib/analytics/utils/sanitize-timezone";
 import { formatMoneyCentsForExport } from "@/lib/api/utils/format-money-cents-for-export";
 import { COMMISSION_EXPORT_COLUMNS } from "@/lib/zod/schemas/commissions";
+import { tz } from "@date-fns/tz";
+import { format } from "date-fns";
 import * as z from "zod/v4";
 import { getCommissions } from "./get-commissions";
 
@@ -29,21 +32,31 @@ const COLUMN_TYPE_SCHEMAS = {
     .nullable()
     .default("")
     .transform((value) => value || ""),
-  date: z
-    .date()
-    .nullable()
-    .transform((date) => (date ? date.toISOString() : "")),
   string: z
     .string()
     .nullable()
     .default("")
     .transform((value) => value || ""),
 };
 
+// Wall-clock time in the export timezone. toISOString() is UTC, so a commission
+// at 2026-10-08 06:59 in Asia/Shanghai was exported as 2026-10-07 22:59:59.
+function exportDateSchema(timezone?: string) {
+  const zone = tz(sanitizeTimezone(timezone));
+
+  return z
+    .date()
+    .nullable()
+    .transform((date) =>
+      date ? format(date, "yyyy-MM-dd HH:mm:ss", { in: zone }) : "",
+    );
+}
+
 // Formats commissions for CSV export with proper column ordering and type coercion
 export function formatCommissionsForExport(
   commissions: Awaited<ReturnType<typeof getCommissions>>,
   columns: string[],
+  timezone?: string,
 ): Record<string, any>[] {
   const sortedColumns = [...columns].sort(
     (a, b) =>
@@ -93,7 +106,11 @@ export function formatCommissionsForExport(
     }
 
     columnSchemas[column] =
-      COLUMN_TYPE_SCHEMAS[columnInfo.type as keyof typeof COLUMN_TYPE_SCHEMAS];
+      columnInfo.type === "date"
+        ? exportDateSchema(timezone)
+        : COLUMN_TYPE_SCHEMAS[
+            columnInfo.type as keyof typeof COLUMN_TYPE_SCHEMAS
+          ];
   }
 
   return z.array(z.object(columnSchemas)).parse(formattedCommissions);

apps/web/tests/commissions/format-commissions-for-export.test.ts

@@ -0,0 +1,77 @@
+import { formatCommissionsForExport } from "@/lib/api/commissions/format-commissions-for-export";
+import { describe, expect, test } from "vitest";
+
+// 2026-10-07 22:59:59 UTC is 2026-10-08 06:59:59 in China (UTC+8), which is the
+// case from the commissions export: the table showed Oct 8 and the CSV showed Oct 7.
+const earlyMorningInChina = new Date("2026-10-07T22:59:59.000Z");
+const paidAt = new Date("2026-10-09T01:02:03.000Z");
+
+function commissionWithDates() {
+  return {
+    id: "cm_1",
+    currency: "usd",
+    amount: 499,
+    earnings: 99,
+    createdAt: earlyMorningInChina,
+    updatedAt: earlyMorningInChina,
+    payout: { paidAt },
+    customer: {
+      name: "Ada",
+      email: "ada@example.com",
+      externalId: null,
+      stripeCustomerId: null,
+    },
+    partner: { name: "Melody", email: "melody@example.com" },
+    programEnrollment: { tenantId: null },
+  } as any;
+}
+
+describe("formatCommissionsForExport", () => {
+  test("formats date columns in the export timezone", () => {
+    const [row] = formatCommissionsForExport(
+      [commissionWithDates()],
+      ["createdAt", "updatedAt", "paidAt"],
+      "Asia/Shanghai",
+    );
+
+    expect(row).toEqual({
+      createdAt: "2026-10-08 06:59:59",
+      updatedAt: "2026-10-08 06:59:59",
+      paidAt: "2026-10-09 09:02:03",
+    });
+  });
+
+  test("formats dates behind UTC in that timezone", () => {
+    const [row] = formatCommissionsForExport(
+      [commissionWithDates()],
+      ["createdAt"],
+      "America/Los_Angeles",
+    );
+
+    // October is PDT (UTC-7).
+    expect(row.createdAt).toBe("2026-10-07 15:59:59");
+  });
+
+  test("falls back to UTC when timezone is missing or invalid", () => {
+    const columns = ["createdAt"];
+    const commissions = [commissionWithDates()];
+
+    expect(formatCommissionsForExport(commissions, columns)[0].createdAt).toBe(
+      "2026-10-07 22:59:59",
+    );
+    expect(
+      formatCommissionsForExport(commissions, columns, "Not/AZone")[0]
+        .createdAt,
+    ).toBe("2026-10-07 22:59:59");
+  });
+
+  test("leaves an empty paid date blank", () => {
+    const [row] = formatCommissionsForExport(
+      [{ ...commissionWithDates(), payout: null }],
+      ["paidAt"],
+      "Asia/Shanghai",
+    );
+
+    expect(row.paidAt).toBe("");
+  });
+});