diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workingday/EffortDuration.java b/navalplanner-business/src/main/java/org/navalplanner/business/workingday/EffortDuration.java
new file mode 100644
index 000000000..cd632c9de
--- /dev/null
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workingday/EffortDuration.java
@@ -0,0 +1,91 @@
+/*
+ * This file is part of NavalPlan
+ *
+ * Copyright (C) 2009-2010 Fundación para o Fomento da Calidade Industrial e
+ *                         Desenvolvemento Tecnolóxico de Galicia
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.navalplanner.business.workingday;
+
+import org.apache.commons.lang.Validate;
+
+public class EffortDuration {
+
+
+    public enum Granularity {
+        HOURS(3600), MINUTES(60), SECONDS(1);
+
+        private final int secondsPerUnit;
+
+        private Granularity(int secondsPerUnit) {
+            this.secondsPerUnit = secondsPerUnit;
+        }
+
+        public int toSeconds(int amount) {
+            return secondsPerUnit * amount;
+        }
+
+        public int convertFromSeconds(int seconds) {
+            return seconds / secondsPerUnit;
+        }
+    }
+
+    public static EffortDuration elapsing(int amount, Granularity granularity) {
+        return new EffortDuration(granularity.toSeconds(amount));
+    }
+
+    private final int seconds;
+
+    private EffortDuration(int seconds) {
+        Validate.isTrue(seconds >= 0, "seconds cannot be negative");
+        this.seconds = seconds;
+    }
+
+    public int getHours() {
+        return convertTo(Granularity.HOURS);
+    }
+
+    public int getMinutes() {
+        return convertTo(Granularity.MINUTES);
+    }
+
+    public int getSeconds() {
+        return convertTo(Granularity.SECONDS);
+    }
+
+    public int convertTo(Granularity granularity) {
+        return granularity.convertFromSeconds(seconds);
+    }
+
+    public EffortDuration and(int amount, Granularity granularity) {
+        return new EffortDuration(seconds + granularity.toSeconds(amount));
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof EffortDuration) {
+            EffortDuration other = (EffortDuration) obj;
+            return getSeconds() == other.getSeconds();
+        }
+        return false;
+    }
+
+    @Override
+    public int hashCode() {
+        return getSeconds();
+    }
+
+}
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/EffortDurationTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/EffortDurationTest.java
new file mode 100644
index 000000000..2c8403ecb
--- /dev/null
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/EffortDurationTest.java
@@ -0,0 +1,97 @@
+/*
+ * This file is part of NavalPlan
+ *
+ * Copyright (C) 2009-2010 Fundación para o Fomento da Calidade Industrial e
+ *                         Desenvolvemento Tecnolóxico de Galicia
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.navalplanner.business.test.workingday;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
+import static org.navalplanner.business.workingday.EffortDuration.elapsing;
+
+import org.junit.Test;
+import org.navalplanner.business.workingday.EffortDuration;
+import org.navalplanner.business.workingday.EffortDuration.Granularity;
+
+public class EffortDurationTest {
+
+    @Test
+    public void itCanExpressTheDurationAsHoursMinutesAndSeconds() {
+        EffortDuration duration = EffortDuration.elapsing(4, Granularity.HOURS);
+        assertThat(duration.getHours(), equalTo(4));
+        assertThat(duration.getMinutes(), equalTo(240));
+        assertThat(duration.getSeconds(), equalTo(240 * 60));
+    }
+
+    @Test
+    public void unitsCannotBeNegative() {
+        Granularity[] granularities = EffortDuration.Granularity.values();
+        for (Granularity each : granularities) {
+            try {
+                EffortDuration.elapsing(-1, each);
+                fail("it should throw IllegalArgumentException");
+            } catch (IllegalArgumentException e) {
+                // ok
+            }
+        }
+    }
+
+    @Test
+    public void hoursCanBeZero() {
+        EffortDuration.elapsing(0, Granularity.HOURS);
+    }
+
+    @Test
+    public void minutesAreTranslatedToHours() {
+        assertThat(elapsing(120, Granularity.MINUTES).getHours(),
+                equalTo(2));
+        assertThat(elapsing(119, Granularity.MINUTES).getHours(), equalTo(1));
+        assertThat(elapsing(121, Granularity.MINUTES).getHours(), equalTo(2));
+    }
+
+    @Test
+    public void canBeTranslatedToAnyGranularity(){
+        assertThat(elapsing(3, Granularity.HOURS)
+                .convertTo(Granularity.MINUTES),
+                equalTo(180));
+    }
+
+    @Test
+    public void canSpecifyADurationWithSeveralUnits() {
+        assertThat(elapsing(2, Granularity.HOURS).and(30, Granularity.MINUTES)
+                .convertTo(Granularity.MINUTES), equalTo(150));
+    }
+
+    private static final EffortDuration oneHourAndAHalf = elapsing(1,
+            Granularity.HOURS).and(30, Granularity.MINUTES);
+    private static final EffortDuration ninetyMinutes = elapsing(90,
+            Granularity.MINUTES);
+
+    @Test
+    public void twoDurationWithTheSameSecondsAreEqual(){
+        assertThat(oneHourAndAHalf, equalTo(ninetyMinutes));
+    }
+
+    @Test
+    public void twoEqualDurationsHaveTheSameHashCode() {
+        assertThat(oneHourAndAHalf.hashCode(),
+                equalTo(ninetyMinutes.hashCode()));
+    }
+
+}