diff --git a/src/main/java/org/gachon/checkmate/domain/post/repository/PostCustomRepositoryImpl.java b/src/main/java/org/gachon/checkmate/domain/post/repository/PostCustomRepositoryImpl.java
index 1fa1e3d..08742b9 100644
--- a/src/main/java/org/gachon/checkmate/domain/post/repository/PostCustomRepositoryImpl.java
+++ b/src/main/java/org/gachon/checkmate/domain/post/repository/PostCustomRepositoryImpl.java
@@ -121,6 +121,6 @@ private BooleanExpression containTextCondition(String text) {
     }
 
     private BooleanExpression validatePostDate() {
-        return post.endDate.before(LocalDate.now());
+        return post.endDate.after(LocalDate.now());
     }
 }
diff --git a/src/main/java/org/gachon/checkmate/domain/post/service/PostService.java b/src/main/java/org/gachon/checkmate/domain/post/service/PostService.java
index 15f8263..68494a4 100644
--- a/src/main/java/org/gachon/checkmate/domain/post/service/PostService.java
+++ b/src/main/java/org/gachon/checkmate/domain/post/service/PostService.java
@@ -47,6 +47,7 @@ public class PostService {
 
     public void createPost(Long userId, PostCreateRequestDto requestDto) {
         validateDuplicateTitle(requestDto.title());
+        validateAvailableEndDate(requestDto.endDate());
         User user = getUserOrThrow(userId);
         Post post = createPostAndSave(requestDto, user);
         createPostCheckListAndSave(requestDto.checkList(), post);
@@ -128,7 +129,7 @@ private int getRateForFrequencyElement(String firstEnumCode, String secondEnumCo
     }
 
     private int getRemainDate(LocalDate endDate) {
-        return (int) endDate.until(LocalDate.now(), ChronoUnit.DAYS);
+        return (int) LocalDate.now().until(endDate, ChronoUnit.DAYS);
     }
 
     private void validateDuplicateTitle(String title) {
@@ -136,6 +137,12 @@ private void validateDuplicateTitle(String title) {
             throw new InvalidValueException(INVALID_POST_TITLE);
     }
 
+    private void validateAvailableEndDate(LocalDate endDate) {
+        LocalDate now = LocalDate.now();
+        if (endDate.isBefore(now))
+            throw new InvalidValueException(INVALID_POST_DATE);
+    }
+
     private Post createPostAndSave(PostCreateRequestDto postCreateRequestDto, User user) {
         Post post = Post.createPost(postCreateRequestDto, user);
         postRepository.save(post);
diff --git a/src/main/java/org/gachon/checkmate/global/error/ErrorCode.java b/src/main/java/org/gachon/checkmate/global/error/ErrorCode.java
index 02fdbe8..c4ea46c 100644
--- a/src/main/java/org/gachon/checkmate/global/error/ErrorCode.java
+++ b/src/main/java/org/gachon/checkmate/global/error/ErrorCode.java
@@ -16,6 +16,7 @@ public enum ErrorCode {
     INVALID_PAGING_SIZE(HttpStatus.BAD_REQUEST, "잘못된 Paging 크기입니다."),
     INVALID_PASSWORD(HttpStatus.BAD_REQUEST, "비밀번호는 8~20자 대소문자 영문, 숫자, 특수문자의 조합이어야 합니다."),
     INVALID_POST_TITLE(HttpStatus.BAD_REQUEST, "이미 존재하는 게시물입니다."),
+    INVALID_POST_DATE(HttpStatus.BAD_REQUEST, "마감시간이 지난 게시물입니다."),
 
     /**
      * 401 Unauthorized
diff --git a/src/main/java/org/gachon/checkmate/global/utils/PagingUtils.java b/src/main/java/org/gachon/checkmate/global/utils/PagingUtils.java
index 81fa48e..4b34d06 100644
--- a/src/main/java/org/gachon/checkmate/global/utils/PagingUtils.java
+++ b/src/main/java/org/gachon/checkmate/global/utils/PagingUtils.java
@@ -14,7 +14,7 @@ public static <T> List<T> convertPaging(List<T> dataList, long page, int size) {
         if (dataList.size() <= page * size)
             throw new InvalidValueException(INVALID_PAGING_SIZE);
         int startIndex = (int) page * size;
-        int endIndex = Math.min(dataList.size(), (int) page * (size + 1));
+        int endIndex = Math.min(dataList.size(), (int) (page + 1) * size);
         return dataList.subList(startIndex, endIndex);
     }
 }