Index: src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java
===================================================================
--- src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java	(revision 655573)
+++ src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java	(working copy)
@@ -226,7 +226,7 @@
     	
     	// Otherwise, check it's only made up, in any case, of:
     	//  y m d h s - / , . :
-    	if(fs.matches("^[yYmMdDhHsS\\-/,. :]+$")) {
+    	if(fs.matches("^[yYmMdDhHsSAP\\-/,. :]+$")) {
     		return true;
     	}