diff --git a/docs/RELEASE-NOTES.md b/docs/RELEASE-NOTES.md
index 386935b..535dc8e 100644
--- a/docs/RELEASE-NOTES.md
+++ b/docs/RELEASE-NOTES.md
@@ -4,6 +4,10 @@
 
 ## [Unreleased]
 
+### 수정
+- cancelQuery idempotent 처리 — 완료된 쿼리 취소 시 에러 대신 정상 응답
+- parseTimestamp 실패 로깅 추가, isNightTimeContact 야간 판정 로직 단순화
+
 ## [2026-03-02.2]
 
 ### 변경
diff --git a/src/main/java/gc/mda/signal_batch/domain/gis/service/AreaSearchService.java b/src/main/java/gc/mda/signal_batch/domain/gis/service/AreaSearchService.java
index b434963..02acce9 100644
--- a/src/main/java/gc/mda/signal_batch/domain/gis/service/AreaSearchService.java
+++ b/src/main/java/gc/mda/signal_batch/domain/gis/service/AreaSearchService.java
@@ -438,6 +438,7 @@ public class AreaSearchService {
         try {
             return Long.parseLong(timestamps.get(index));
         } catch (NumberFormatException e) {
+            log.warn("Invalid timestamp at index {}: {}", index, timestamps.get(index));
             return 0L;
         }
     }
diff --git a/src/main/java/gc/mda/signal_batch/domain/gis/service/VesselContactService.java b/src/main/java/gc/mda/signal_batch/domain/gis/service/VesselContactService.java
index 047aa6c..8b0f357 100644
--- a/src/main/java/gc/mda/signal_batch/domain/gis/service/VesselContactService.java
+++ b/src/main/java/gc/mda/signal_batch/domain/gis/service/VesselContactService.java
@@ -360,27 +360,15 @@ public class VesselContactService {
      * 접촉 구간이 22:00~06:00 KST에 포함되는지 판단.
      */
     private boolean isNightTimeContact(long contactStartSec, long contactEndSec) {
-        Instant startInstant = Instant.ofEpochSecond(contactStartSec);
-        Instant endInstant = Instant.ofEpochSecond(contactEndSec);
+        ZonedDateTime startKst = Instant.ofEpochSecond(contactStartSec).atZone(KST);
+        ZonedDateTime endKst = Instant.ofEpochSecond(contactEndSec).atZone(KST);
 
-        ZonedDateTime startKst = startInstant.atZone(KST);
-        ZonedDateTime endKst = endInstant.atZone(KST);
-
-        // 접촉 구간 내 모든 날짜에 대해 야간 시간대 겹침 체크
+        // 각 날짜의 야간 구간(22:00~익일 06:00)과 접촉 구간 겹침 체크
         LocalDate day = startKst.toLocalDate();
-        LocalDate lastDay = endKst.toLocalDate().plusDays(1);
-
-        while (!day.isAfter(lastDay)) {
-            // 해당 날짜의 야간: 전날 22:00 ~ 당일 06:00
-            ZonedDateTime nightStart = day.atTime(LocalTime.of(22, 0)).atZone(KST).minusDays(1);
-            ZonedDateTime nightEnd = day.atTime(LocalTime.of(6, 0)).atZone(KST);
-
-            // 당일 22:00 ~ 다음날 06:00
-            ZonedDateTime nightStart2 = day.atTime(LocalTime.of(22, 0)).atZone(KST);
-            ZonedDateTime nightEnd2 = day.plusDays(1).atTime(LocalTime.of(6, 0)).atZone(KST);
-
-            if (isOverlapping(startKst, endKst, nightStart, nightEnd)
-                    || isOverlapping(startKst, endKst, nightStart2, nightEnd2)) {
+        while (!day.isAfter(endKst.toLocalDate())) {
+            ZonedDateTime nightStart = day.atTime(22, 0).atZone(KST);
+            ZonedDateTime nightEnd = day.plusDays(1).atTime(6, 0).atZone(KST);
+            if (startKst.isBefore(nightEnd) && endKst.isAfter(nightStart)) {
                 return true;
             }
             day = day.plusDays(1);
@@ -388,11 +376,6 @@ public class VesselContactService {
         return false;
     }
 
-    private boolean isOverlapping(ZonedDateTime s1, ZonedDateTime e1,
-                                  ZonedDateTime s2, ZonedDateTime e2) {
-        return s1.isBefore(e2) && s2.isBefore(e1);
-    }
-
     // ── 추정 속도 계산 ──
 
     /**
diff --git a/src/main/java/gc/mda/signal_batch/global/websocket/controller/StompTrackController.java b/src/main/java/gc/mda/signal_batch/global/websocket/controller/StompTrackController.java
index 05ccc55..1b75ad8 100644
--- a/src/main/java/gc/mda/signal_batch/global/websocket/controller/StompTrackController.java
+++ b/src/main/java/gc/mda/signal_batch/global/websocket/controller/StompTrackController.java
@@ -113,10 +113,9 @@ public class StompTrackController {
             trackStreamingService.cancelQuery(queryId);
             chunkedTrackStreamingService.cancelQuery(queryId);
             activeSessions.remove(sessionId);
-            return QueryResponse.cancelled(queryId);
         }
-        
-        return QueryResponse.error(queryId, "Query not found");
+        // 세션 없어도 취소 성공 반환 (idempotent — 이미 완료/취소된 쿼리)
+        return QueryResponse.cancelled(queryId);
     }
 
     /**