diff --git a/routes/calendar.cts b/routes/calendar.cts
index 5cab533..5795d1a 100644
--- a/routes/calendar.cts
+++ b/routes/calendar.cts
@@ -1,7 +1,7 @@
 // @ts-nocheck — route controller converted to .cts; handler req/res typed, full type-check deferred (thin glue over typed services).
 import type { Req, Res, Next } from '../types/http';
 const express = require('express');
-const { standardizeError } = require('../middleware/errorFormatter.cts');
+const { ValidationError } = require('../utils/apiError.cts');
 const router = express.Router();
 const { getDb } = require('../db/database.cts');
 const { buildTrackerRow, getCycleRange } = require('../services/statusService.cts');
@@ -104,22 +104,10 @@ router.get('/', (req: Req, res: Res) => {
   const month = parseInt(req.query.month || now.getMonth() + 1, 10);
 
   if (isNaN(year) || year < 2000 || year > 2100) {
-    return res
-      .status(400)
-      .json(
-        standardizeError(
-          'year must be a 4-digit integer between 2000 and 2100',
-          'VALIDATION_ERROR',
-          'year',
-        ),
-      );
+    throw ValidationError('year must be a 4-digit integer between 2000 and 2100', 'year');
   }
   if (isNaN(month) || month < 1 || month > 12) {
-    return res
-      .status(400)
-      .json(
-        standardizeError('month must be an integer between 1 and 12', 'VALIDATION_ERROR', 'month'),
-      );
+    throw ValidationError('month must be an integer between 1 and 12', 'month');
   }
 
   const today = localDateString(now);