diff --git a/src/java/org/apache/poi/ss/usermodel/DateUtil.java b/src/java/org/apache/poi/ss/usermodel/DateUtil.java
index 12e862d4d..2a32e4721 100644
--- a/src/java/org/apache/poi/ss/usermodel/DateUtil.java
+++ b/src/java/org/apache/poi/ss/usermodel/DateUtil.java
@@ -55,7 +55,8 @@ public class DateUtil {
      */
     private static final Pattern date_ptrn1 = Pattern.compile("^\\[\\$\\-.*?\\]");
     private static final Pattern date_ptrn2 = Pattern.compile("^\\[[a-zA-Z]+\\]");
-    private static final Pattern date_ptrn3 = Pattern.compile("^[\\[\\]yYmMdDhHsS\\-/,. :\"\\\\]+0*[ampAMP/]*$");
+    private static final Pattern date_ptrn3a = Pattern.compile("[yYmMdDhHsS]");
+    private static final Pattern date_ptrn3b = Pattern.compile("^[\\[\\]yYmMdDhHsS\\-/,. :\"\\\\]+0*[ampAMP/]*$");
     //  elapsed time patterns: [h],[m] and [s]
     private static final Pattern date_ptrn4 = Pattern.compile("^\\[([hH]+|[mM]+|[sS]+)\\]");
 
@@ -364,10 +365,16 @@ public class DateUtil {
            fs = fs.substring(0, fs.indexOf(';'));
         }
 
-        // Otherwise, check it's only made up, in any case, of:
-        //  y m d h s - \ / , . :
+        // Ensure it has some date letters in it
+        // (Avoids false positives on the rest of pattern 3)
+        if (! date_ptrn3a.matcher(fs).find()) {
+           return false;
+        }
+        
+        // If we get here, check it's only made up, in any case, of:
+        //  y m d h s - \ / , . : [ ]
         // optionally followed by AM/PM
-        return date_ptrn3.matcher(fs).matches();
+        return date_ptrn3b.matcher(fs).matches();
     }
 
     /**
diff --git a/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java b/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java
index 32f3fe65f..6733f73fa 100644
--- a/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java
+++ b/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java
@@ -499,5 +499,14 @@ public final class TestHSSFDateUtil extends TestCase {
         assertEquals(valueToTest.getTime(), returnedValue.getTime());
     }
 
-
+    /**
+     * DateUtil.isCellFormatted(Cell) should not true for a numeric cell 
+     * that's formatted as ".0000"
+     */
+    public void testBug54557() throws Exception {
+       final String format = ".0000";
+       boolean isDateFormat = HSSFDateUtil.isADateFormat(165, format);
+       
+       assertEquals(false, isDateFormat);
+    }
 }