diff --git a/include/svl/zforlist.hxx b/include/svl/zforlist.hxx
index 50e7ea3ca4986..d87641e468431 100644
--- a/include/svl/zforlist.hxx
+++ b/include/svl/zforlist.hxx
@@ -74,6 +74,7 @@ namespace com { namespace sun { namespace star {
 
     Do NOT insert any new values!
     The values here correspond with those in offapi/com/sun/star/i18n/NumberFormatIndex.idl
+    You may append values though.
  */
 enum NfIndexTableOffset
 {
@@ -131,6 +132,7 @@ enum NfIndexTableOffset
     NF_DATE_DIN_MMDD,                       // 10-08                        DIN
     NF_DATE_DIN_YYMMDD,                     // 97-10-08                     DIN
     NF_DATE_DIN_YYYYMMDD,                   // 1997-10-08                   DIN
+    NF_DATE_ISO_YYYYMMDD = NF_DATE_DIN_YYYYMMDD, // 1997-10-08              ISO clarify with name
     NF_DATE_SYS_MMYY,                       // 10.97
     NF_DATE_SYS_DDMMM,                      // 08.Oct
     NF_DATE_MMMM,                           // October
@@ -156,15 +158,26 @@ enum NfIndexTableOffset
     NF_BOOLEAN,                             // BOOLEAN
     NF_TEXT,                                // @
 
-    NF_INDEX_TABLE_LOCALE_DATA_DEFAULTS,    // old number of predefined entries, locale data additions start after this
+    NF_INDEX_TABLE_LOCALE_DATA_DEFAULTS,    // == 50, old number of predefined entries, i18npool locale data additions start after this
 
     // From here on are values of new built-in formats that are not in the
     // original NumberFormatIndex.idl
 
+    // XXX Values appended here must also get a corresponding entry in
+    // svl/source/numbers/zforlist.cxx indexTable[] in the same order.
+
+    // XXX The dialog's number format shell assumes start/end spans
+    // (NF_..._START and NF_..._END above) to fill its categories with builtin
+    // formats, make new formats known to svx/source/items/numfmtsh.cxx
+    // SvxNumberFormatShell::FillEListWithStd_Impl(), otherwise they will not
+    // be be listed at all. Yes that is ugly.
+
     NF_FRACTION_3 = NF_INDEX_TABLE_LOCALE_DATA_DEFAULTS,    // # ?/4
     NF_FRACTION_4,                          // # ?/100
 
-    NF_INDEX_TABLE_ENTRIES
+    NF_DATETIME_ISO_YYYYMMDD_HHMMSS,        // 1997-10-08 01:23:45          ISO (with blank instead of T)
+
+    NF_INDEX_TABLE_ENTRIES                  // == 53, reserved up to 59 to not use in i18npool locale data.
 };
 
 
diff --git a/svl/source/numbers/zforlist.cxx b/svl/source/numbers/zforlist.cxx
index 91037ff09f864..df13480ff0191 100644
--- a/svl/source/numbers/zforlist.cxx
+++ b/svl/source/numbers/zforlist.cxx
@@ -91,6 +91,7 @@ using namespace ::std;
  * (old currency) is recognized as a date (#53155#). */
 #define UNKNOWN_SUBSTITUTE      LANGUAGE_ENGLISH_US
 
+// Same order as in include/svl/zforlist.hxx enum NfIndexTableOffset
 static sal_uInt32 const indexTable[NF_INDEX_TABLE_ENTRIES] = {
     ZF_STANDARD, // NF_NUMBER_STANDARD
     ZF_STANDARD + 1, // NF_NUMBER_INT
@@ -143,7 +144,8 @@ static sal_uInt32 const indexTable[NF_INDEX_TABLE_ENTRIES] = {
     ZF_STANDARD_LOGICAL, // NF_BOOLEAN
     ZF_STANDARD_TEXT, // NF_TEXT
     ZF_STANDARD_FRACTION + 2, // NF_FRACTION_3
-    ZF_STANDARD_FRACTION + 3 // NF_FRACTION_4
+    ZF_STANDARD_FRACTION + 3, // NF_FRACTION_4
+    ZF_STANDARD_DATETIME + 2 // NF_DATETIME_ISO_YYYYMMDD_HHMMSS
 };
 
 /**
@@ -2495,7 +2497,7 @@ void SvNumberFormatter::ImpGenerateFormats( sal_uInt32 CLOffset, bool bNoAdditio
     ImpInsertFormat( aFormatSeq[nIdx],
                      CLOffset + ZF_STANDARD_NEWEXTENDED_DATE_DIN_YYMMDD /* NF_DATE_DIN_YYMMDD */ );
 
-    // YYYY-MM-DD   DIN/EN
+    // YYYY-MM-DD   DIN/EN/ISO
     nIdx = ImpGetFormatCodeIndex( aFormatSeq, NF_DATE_DIN_YYYYMMDD );
     ImpInsertFormat( aFormatSeq[nIdx],
                      CLOffset + ZF_STANDARD_NEWEXTENDED_DATE_DIN_YYYYMMDD /* NF_DATE_DIN_YYYYMMDD */ );
@@ -2555,6 +2557,22 @@ void SvNumberFormatter::ImpGenerateFormats( sal_uInt32 CLOffset, bool bNoAdditio
     ImpInsertFormat( aFormatSeq[nIdx],
                      CLOffset + ZF_STANDARD_DATETIME+1 /* NF_DATETIME_SYS_DDMMYYYY_HHMMSS */ );
 
+    const NfKeywordTable & rKeyword = pFormatScanner->GetKeywords();
+    i18n::NumberFormatCode aSingleFormatCode;
+    OUStringBuffer aBuf;
+    aSingleFormatCode.Usage = i18n::KNumberFormatUsage::DATE_TIME;
+
+    // YYYY-MM-DD HH:MM:SS   ISO
+    aBuf.append( rKeyword[NF_KEY_YYYY]).append('-').
+        append( rKeyword[NF_KEY_MM]).append('-').
+        append( rKeyword[NF_KEY_DD]).append(' ').
+        append( rKeyword[NF_KEY_HH]).append(':').
+        append( rKeyword[NF_KEY_MMI]).append(':').
+        append( rKeyword[NF_KEY_SS]);
+    aSingleFormatCode.Code = aBuf.makeStringAndClear();
+    ImpInsertFormat( aSingleFormatCode,
+                     CLOffset + ZF_STANDARD_DATETIME+2 /* NF_DATETIME_ISO_YYYYMMDD_HHMMSS */ );
+
 
     // Scientific number
     aFormatSeq = aNumberFormatCode.getAllFormatCode( i18n::KNumberFormatUsage::SCIENTIFIC_NUMBER );
@@ -2572,7 +2590,6 @@ void SvNumberFormatter::ImpGenerateFormats( sal_uInt32 CLOffset, bool bNoAdditio
 
 
     // Fraction number (no default option)
-    i18n::NumberFormatCode aSingleFormatCode;
     aSingleFormatCode.Usage = i18n::KNumberFormatUsage::FRACTION_NUMBER;
 
      // # ?/?
@@ -2598,7 +2615,6 @@ void SvNumberFormatter::ImpGenerateFormats( sal_uInt32 CLOffset, bool bNoAdditio
 
 
     // Week of year
-    const NfKeywordTable & rKeyword = pFormatScanner->GetKeywords();
     aSingleFormatCode.Code = rKeyword[NF_KEY_WW];
     ImpInsertFormat( aSingleFormatCode,
                      CLOffset + ZF_STANDARD_NEWEXTENDED_DATE_WW /* NF_DATE_WW */ );
diff --git a/svx/source/items/numfmtsh.cxx b/svx/source/items/numfmtsh.cxx
index d4d664991210d..b4a4fc2cad6a1 100644
--- a/svx/source/items/numfmtsh.cxx
+++ b/svx/source/items/numfmtsh.cxx
@@ -621,6 +621,8 @@ void SvxNumberFormatShell::FillEListWithStd_Impl( std::vector<OUString>& rList,
         if(nPrivCat==CAT_DATE || nPrivCat==CAT_TIME)
         {
             nSelPos=FillEListWithDateTime_Impl(rList,nSelPos);
+            nSelPos = FillEListWithFormats_Impl( rList, nSelPos,
+                    NF_DATETIME_ISO_YYYYMMDD_HHMMSS, NF_DATETIME_ISO_YYYYMMDD_HHMMSS);
         }
     }
 }