diff --git a/fesod-sheet/src/main/java/org/apache/fesod/sheet/util/ExcelDateFormatDetector.java b/fesod-sheet/src/main/java/org/apache/fesod/sheet/util/ExcelDateFormatDetector.java
index b144e2d43..4ff14f2aa 100644
--- a/fesod-sheet/src/main/java/org/apache/fesod/sheet/util/ExcelDateFormatDetector.java
+++ b/fesod-sheet/src/main/java/org/apache/fesod/sheet/util/ExcelDateFormatDetector.java
@@ -35,7 +35,7 @@ class ExcelDateFormatDetector {
     /**
      * Is a cache of dates
      */
-    private static final ThreadLocal<Map<Short, Boolean>> DATE_THREAD_LOCAL = new ThreadLocal<>();
+    private static final ThreadLocal<Map<String, Boolean>> DATE_THREAD_LOCAL = new ThreadLocal<>();
 
     /**
      * The following patterns are used in {@link #isADateFormat(Short, String)}
@@ -67,21 +67,27 @@ static boolean isADateFormat(Short formatIndex, String formatString) {
         if (formatIndex == null) {
             return false;
         }
-        Map<Short, Boolean> isDateCache = DATE_THREAD_LOCAL.get();
+        // Format indexes are defined per workbook, so the same index can map to different format strings.
+        final String cacheKey = cacheKey(formatIndex, formatString);
+        Map<String, Boolean> isDateCache = DATE_THREAD_LOCAL.get();
         if (isDateCache == null) {
             isDateCache = MapUtils.newHashMap();
             DATE_THREAD_LOCAL.set(isDateCache);
         } else {
-            Boolean isDatecachedDataList = isDateCache.get(formatIndex);
+            Boolean isDatecachedDataList = isDateCache.get(cacheKey);
             if (isDatecachedDataList != null) {
                 return isDatecachedDataList;
             }
         }
         boolean isDate = isADateFormatUncached(formatIndex, formatString);
-        isDateCache.put(formatIndex, isDate);
+        isDateCache.put(cacheKey, isDate);
         return isDate;
     }
 
+    private static String cacheKey(Short formatIndex, String formatString) {
+        return formatIndex + "\u0000" + (formatString == null ? "" : formatString);
+    }
+
     /**
      * Determine if it is a date format.
      *
diff --git a/fesod-sheet/src/test/java/org/apache/fesod/sheet/util/DateUtilsTest.java b/fesod-sheet/src/test/java/org/apache/fesod/sheet/util/DateUtilsTest.java
index c9b43c3e4..ccad06474 100644
--- a/fesod-sheet/src/test/java/org/apache/fesod/sheet/util/DateUtilsTest.java
+++ b/fesod-sheet/src/test/java/org/apache/fesod/sheet/util/DateUtilsTest.java
@@ -528,6 +528,7 @@ void test_isADateFormat_false(String formatString) {
         Assertions.assertFalse(DateUtils.isADateFormat(null, formatString));
     }
 
+    @SuppressWarnings("unchecked")
     @Test
     void test_isADateFormat_Cache() throws NoSuchFieldException, IllegalAccessException {
         short formatId = 200;
@@ -538,15 +539,49 @@ void test_isADateFormat_Cache() throws NoSuchFieldException, IllegalAccessExcept
 
         Field threadLocalField = ExcelDateFormatDetector.class.getDeclaredField("DATE_THREAD_LOCAL");
         threadLocalField.setAccessible(true);
-        ThreadLocal<Map<Short, Boolean>> tl = (ThreadLocal<Map<Short, Boolean>>) threadLocalField.get(null);
+        ThreadLocal<Map<String, Boolean>> tl = (ThreadLocal<Map<String, Boolean>>) threadLocalField.get(null);
 
-        Map<Short, Boolean> cache = tl.get();
+        Map<String, Boolean> cache = tl.get();
         Assertions.assertNotNull(cache);
-        Assertions.assertTrue(cache.containsKey(formatId));
-        Assertions.assertTrue(cache.get(formatId));
+        Assertions.assertEquals(1, cache.size());
+        Assertions.assertEquals(Boolean.TRUE, cache.get(formatId + "\u0000" + formatStr));
 
         boolean res2 = DateUtils.isADateFormat(formatId, formatStr);
         Assertions.assertTrue(res2);
+        Assertions.assertEquals(1, cache.size());
+    }
+
+    @Test
+    void test_isADateFormat_cacheDistinguishesFormatStrings() {
+        short formatId = 201;
+
+        Assertions.assertTrue(DateUtils.isADateFormat(formatId, "yyyy-mm-dd"));
+        Assertions.assertFalse(DateUtils.isADateFormat(formatId, "0.00"));
+        Assertions.assertTrue(DateUtils.isADateFormat(formatId, "yyyy-mm-dd"));
+    }
+
+    @Test
+    void test_isADateFormat_cacheDistinguishesFormatStringsInReverseOrder() {
+        short formatId = 202;
+
+        Assertions.assertFalse(DateUtils.isADateFormat(formatId, "0.00"));
+        Assertions.assertTrue(DateUtils.isADateFormat(formatId, "yyyy-mm-dd"));
+    }
+
+    @Test
+    void test_isADateFormat_cacheDistinguishesNullFormatString() {
+        short formatId = 203;
+
+        Assertions.assertTrue(DateUtils.isADateFormat(formatId, "yyyy-mm-dd"));
+        Assertions.assertFalse(DateUtils.isADateFormat(formatId, null));
+    }
+
+    @Test
+    void test_isADateFormat_internalIndexStillOverridesFormatString() {
+        short internalFormatId = 0x0e;
+
+        Assertions.assertTrue(DateUtils.isADateFormat(internalFormatId, "0.00"));
+        Assertions.assertFalse(DateUtils.isADateFormat((short) (0x0e + 100), "0.00"));
     }
 
     @Test