diff --git a/backend/src/main/java/ervu_business_metrics/util/DateUtils.java b/backend/src/main/java/ervu_business_metrics/util/DateUtils.java
index a8d13d1..eb65126 100644
--- a/backend/src/main/java/ervu_business_metrics/util/DateUtils.java
+++ b/backend/src/main/java/ervu_business_metrics/util/DateUtils.java
@@ -18,7 +18,7 @@ public final class DateUtils {
 
   public static String getFormattedClientDate(Timestamp timestamp, String clientTimeZone) {
     if (timestamp == null) {
-      return "";
+      throw new IllegalArgumentException("Timestamp parameter is required");
     }
 
     ZoneId zoneId;