diff --git a/src/config/env.ts b/src/config/env.ts
index 4f63cff..402f6b7 100644
--- a/src/config/env.ts
+++ b/src/config/env.ts
@@ -1,6 +1,9 @@
 import dotenv from 'dotenv';
 dotenv.config();
 
+// Set timezone for Date operations — all attendance/time records are in Czech local time
+process.env.TZ = process.env.TZ || 'Europe/Prague';
+
 function required(key: string): string {
   const val = process.env[key];
   if (!val) throw new Error(`Missing required env variable: ${key}`);