diff --git a/src/java/org/apache/poi/hssf/record/formula/atp/AnalysisToolPak.java b/src/java/org/apache/poi/hssf/record/formula/atp/AnalysisToolPak.java
index 60f06695d..f46b4aea7 100644
--- a/src/java/org/apache/poi/hssf/record/formula/atp/AnalysisToolPak.java
+++ b/src/java/org/apache/poi/hssf/record/formula/atp/AnalysisToolPak.java
@@ -109,8 +109,8 @@ public final class AnalysisToolPak {
 		r(m, "IMSUB", null);
 		r(m, "IMSUM", null);
 		r(m, "INTRATE", null);
-		r(m, "ISEVEN", null);
-		r(m, "ISODD", null);
+		r(m, "ISEVEN", ParityFunction.IS_EVEN);
+		r(m, "ISODD", ParityFunction.IS_ODD);
 		r(m, "LCM", null);
 		r(m, "MDURATION", null);
 		r(m, "MROUND", null);
diff --git a/src/java/org/apache/poi/hssf/record/formula/atp/ParityFunction.java b/src/java/org/apache/poi/hssf/record/formula/atp/ParityFunction.java
new file mode 100644
index 000000000..dd9ecc2af
--- /dev/null
+++ b/src/java/org/apache/poi/hssf/record/formula/atp/ParityFunction.java
@@ -0,0 +1,74 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+package org.apache.poi.hssf.record.formula.atp;
+
+import org.apache.poi.hssf.record.formula.eval.BlankEval;
+import org.apache.poi.hssf.record.formula.eval.BoolEval;
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.Eval;
+import org.apache.poi.hssf.record.formula.eval.EvaluationException;
+import org.apache.poi.hssf.record.formula.eval.OperandResolver;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+import org.apache.poi.hssf.record.formula.functions.FreeRefFunction;
+import org.apache.poi.hssf.usermodel.HSSFSheet;
+import org.apache.poi.hssf.usermodel.HSSFWorkbook;
+/**
+ * Implementation of Excel 'Analysis ToolPak' function ISEVEN() ISODD()<br/>
+ * 
+ * @author Josh Micich
+ */
+final class ParityFunction implements FreeRefFunction {
+
+	public static final FreeRefFunction IS_EVEN = new ParityFunction(0);
+	public static final FreeRefFunction IS_ODD = new ParityFunction(1);
+	private final int _desiredParity;
+	
+	private ParityFunction(int desiredParity) {
+		_desiredParity = desiredParity;
+	}
+
+	public ValueEval evaluate(Eval[] args, int srcCellRow, short srcCellCol, HSSFWorkbook workbook,
+			HSSFSheet sheet) {
+		if (args.length != 1) {
+			return ErrorEval.VALUE_INVALID;  
+		}
+		
+		int val;
+		try {
+			val = evaluateArgParity(args[0], srcCellRow, srcCellCol);
+		} catch (EvaluationException e) {
+			return e.getErrorEval();
+		}
+
+		return BoolEval.valueOf(val == _desiredParity);
+	}
+
+	private static int evaluateArgParity(Eval arg, int srcCellRow, short srcCellCol) throws EvaluationException {
+		ValueEval ve = OperandResolver.getSingleValue(arg, srcCellRow, srcCellCol);
+		
+		if (ve == BlankEval.INSTANCE) {
+			return 0;
+		}
+		double d = OperandResolver.coerceValueToDouble(ve);
+		if (d < 0) {
+			d = -d;
+		}
+		long v = (long) Math.floor(d);
+		return (int) (v & 0x0001);
+	}
+}
diff --git a/src/java/org/apache/poi/hssf/record/formula/atp/YearFrac.java b/src/java/org/apache/poi/hssf/record/formula/atp/YearFrac.java
index 586187192..ac196723e 100644
--- a/src/java/org/apache/poi/hssf/record/formula/atp/YearFrac.java
+++ b/src/java/org/apache/poi/hssf/record/formula/atp/YearFrac.java
@@ -21,6 +21,7 @@ import java.util.Calendar;
 import java.util.GregorianCalendar;
 import java.util.regex.Pattern;
 
+import org.apache.poi.hssf.record.formula.eval.BlankEval;
 import org.apache.poi.hssf.record.formula.eval.ErrorEval;
 import org.apache.poi.hssf.record.formula.eval.Eval;
 import org.apache.poi.hssf.record.formula.eval.EvaluationException;
@@ -96,6 +97,9 @@ final class YearFrac implements FreeRefFunction {
 			Calendar date = parseDate(strVal);
 			return HSSFDateUtil.getExcelDate(date, false);
 		}
+		if (ve instanceof BlankEval) {
+			return 0.0;
+		}
 		return OperandResolver.coerceValueToDouble(ve);
 	}
 
@@ -120,7 +124,7 @@ final class YearFrac implements FreeRefFunction {
 		} catch (NumberFormatException e) {
 			throw new EvaluationException(ErrorEval.VALUE_INVALID);
 		}
-		if (f0<0 || f1<0 || f2<0 || f0>12 || f1>12 || f2>12) {
+		if (f0<0 || f1<0 || f2<0 || (f0>12 && f1>12 && f2>12)) {
 			// easy to see this cannot be a valid date
 			throw new EvaluationException(ErrorEval.VALUE_INVALID);
 		}
@@ -150,6 +154,7 @@ final class YearFrac implements FreeRefFunction {
 		if (day <1 || day>cal.getActualMaximum(Calendar.DAY_OF_MONTH)) {
 			throw new EvaluationException(ErrorEval.VALUE_INVALID);
 		}
+		cal.set(Calendar.DAY_OF_MONTH, day);
 		return cal;
 	}
 
diff --git a/src/testcases/org/apache/poi/hssf/data/externalFunctionExample.xls b/src/testcases/org/apache/poi/hssf/data/externalFunctionExample.xls
index 07eafb414..fc81e60a1 100755
Binary files a/src/testcases/org/apache/poi/hssf/data/externalFunctionExample.xls and b/src/testcases/org/apache/poi/hssf/data/externalFunctionExample.xls differ
diff --git a/src/testcases/org/apache/poi/hssf/record/formula/TestExternalFunctionFormulas.java b/src/testcases/org/apache/poi/hssf/record/formula/TestExternalFunctionFormulas.java
index 2b60e23c3..b3a82c6de 100755
--- a/src/testcases/org/apache/poi/hssf/record/formula/TestExternalFunctionFormulas.java
+++ b/src/testcases/org/apache/poi/hssf/record/formula/TestExternalFunctionFormulas.java
@@ -74,9 +74,18 @@ public final class TestExternalFunctionFormulas extends TestCase {
 	public void testEvaluate() {
 		HSSFWorkbook wb = HSSFTestDataSamples.openSampleWorkbook("externalFunctionExample.xls");
 		HSSFSheet sheet = wb.getSheetAt(0);
-		HSSFCell cell = sheet.getRow(0).getCell(0);
 		HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(sheet, wb);
-		CellValue evalResult = fe.evaluate(cell);
-		evalResult.toString();
+		confirmCellEval(sheet, 0, 0, fe, "YEARFRAC(B1,C1)", 29.0/90.0);
+		confirmCellEval(sheet, 1, 0, fe, "YEARFRAC(B2,C2)", 0.0);
+		confirmCellEval(sheet, 2, 0, fe, "IF(ISEVEN(3),1.2,1.6)", 1.6);
+		confirmCellEval(sheet, 3, 0, fe, "IF(ISODD(3),1.2,1.6)", 1.2);
+	}
+
+	private static void confirmCellEval(HSSFSheet sheet, int rowIx, int colIx, 
+			HSSFFormulaEvaluator fe, String expectedFormula, double expectedResult) {
+		HSSFCell cell = sheet.getRow(rowIx).getCell(colIx);
+		assertEquals(expectedFormula, cell.getCellFormula());
+		CellValue cv = fe.evaluate(cell);
+		assertEquals(expectedResult, cv.getNumberValue(), 0.0);
 	}
 }
diff --git a/src/testcases/org/apache/poi/hssf/record/formula/atp/TestYearFracCalculator.java b/src/testcases/org/apache/poi/hssf/record/formula/atp/TestYearFracCalculator.java
index aaf03a238..890a5c2cb 100644
--- a/src/testcases/org/apache/poi/hssf/record/formula/atp/TestYearFracCalculator.java
+++ b/src/testcases/org/apache/poi/hssf/record/formula/atp/TestYearFracCalculator.java
@@ -38,6 +38,7 @@ public final class TestYearFracCalculator extends TestCase {
 		confirm(md(1999, 3, 31), md(1999, 4, 3), 1, 0.008219178);
 		confirm(md(1999, 4, 5), md(1999, 4, 8), 1, 0.008219178);
 		confirm(md(1999, 4, 4), md(1999, 4, 7), 1, 0.008219178);
+		confirm(md(2000, 2, 5), md(2000, 6, 1), 0, 0.322222222);
 	}
 
 	private void confirm(double startDate, double endDate, int basis, double expectedValue) {