diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java
index 1045931df..5870f6c05 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/BaseCalendar.java
@@ -23,6 +23,7 @@ package org.navalplanner.business.calendars.entities;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Date;
+import java.util.EnumMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -37,6 +38,8 @@ import org.navalplanner.business.calendars.daos.IBaseCalendarDAO;
 import org.navalplanner.business.calendars.entities.CalendarData.Days;
 import org.navalplanner.business.common.IntegrationEntity;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
+import org.navalplanner.business.workingday.EffortDuration;
+import org.navalplanner.business.workingday.EffortDuration.Granularity;
 import org.navalplanner.business.workingday.ResourcesPerDay;
 
 /**
@@ -886,11 +889,30 @@ public class BaseCalendar extends IntegrationEntity implements IWorkHours {
         calendarAvailability.setEndDate(endDate);
     }
 
+    public static int roundToHours(EffortDuration effortDuration) {
+        if (effortDuration.equals(EffortDuration.zero())) {
+            return 0;
+        }
+        return Math.max(1, roundHalfUpToHours(effortDuration.decompose()));
+    }
+
+    private static int roundHalfUpToHours(
+            EnumMap<Granularity, Integer> components) {
+        int seconds = components.get(Granularity.SECONDS);
+        int minutes = components.get(Granularity.MINUTES)
+                + (seconds < 30 ? 0 : 1);
+        int hours = components.get(Granularity.HOURS) + (minutes < 30 ? 0 : 1);
+        return hours;
+    }
+
     @Override
     public Integer toHours(LocalDate day, ResourcesPerDay resourcesPerDay) {
         final Integer workableHours = getWorkableHours(day);
-        return limitOverAssignability(day, resourcesPerDay
-                .asHoursGivenResourceWorkingDayOf(workableHours), workableHours);
+        return limitOverAssignability(day,
+                roundToHours(resourcesPerDay
+                        .asDurationGivenWorkingDayOf(EffortDuration
+                                .hours(workableHours))),
+                workableHours);
     }
 
     private Integer limitOverAssignability(LocalDate day,
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/SameWorkHoursEveryDay.java b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/SameWorkHoursEveryDay.java
index ab3e214a6..6fa1e4193 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/SameWorkHoursEveryDay.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/calendars/entities/SameWorkHoursEveryDay.java
@@ -22,6 +22,7 @@ package org.navalplanner.business.calendars.entities;
 
 import org.apache.commons.lang.Validate;
 import org.joda.time.LocalDate;
+import org.navalplanner.business.workingday.EffortDuration;
 import org.navalplanner.business.workingday.ResourcesPerDay;
 
 public class SameWorkHoursEveryDay implements IWorkHours {
@@ -47,7 +48,9 @@ public class SameWorkHoursEveryDay implements IWorkHours {
 
     @Override
     public Integer toHours(LocalDate day, ResourcesPerDay amount) {
-        return amount.asHoursGivenResourceWorkingDayOf(getCapacityAt(day));
+        return BaseCalendar.roundToHours(amount
+                .asDurationGivenWorkingDayOf(EffortDuration
+                        .hours(getCapacityAt(day))));
     }
 
     @Override
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workingday/ResourcesPerDay.java b/navalplanner-business/src/main/java/org/navalplanner/business/workingday/ResourcesPerDay.java
index 3b4484ac3..60a55af61 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/workingday/ResourcesPerDay.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workingday/ResourcesPerDay.java
@@ -25,6 +25,7 @@ import java.math.RoundingMode;
 
 import org.apache.commons.lang.Validate;
 import org.navalplanner.business.common.ProportionalDistributor;
+import org.navalplanner.business.workingday.EffortDuration.Granularity;
 
 public class ResourcesPerDay {
 
@@ -99,15 +100,16 @@ public class ResourcesPerDay {
         return amount;
     }
 
-    public int asHoursGivenResourceWorkingDayOf(
-            Integer resourceWorkingDayHours) {
+    public EffortDuration asDurationGivenWorkingDayOf(
+            EffortDuration resourceWorkingDayDuration) {
         BigDecimal multiply = getAmount().multiply(
-                new BigDecimal(resourceWorkingDayHours));
-        if(multiply.compareTo(BigDecimal.ZERO)>0){
-            return Math.max(1, multiply.setScale(0, RoundingMode.HALF_UP)
-                    .intValue());
+                new BigDecimal(resourceWorkingDayDuration.getSeconds()));
+        if (multiply.compareTo(BigDecimal.ZERO) > 0) {
+            return EffortDuration.elapsing(Math.max(1,
+                    multiply.setScale(0, RoundingMode.HALF_UP).intValue()),
+                    Granularity.SECONDS);
         } else {
-            return 0;
+            return EffortDuration.zero();
         }
     }
 
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java
index 70af2fc88..c8edbe04d 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/GenericResourceAllocationTest.java
@@ -60,6 +60,7 @@ import org.navalplanner.business.resources.entities.Resource;
 import org.navalplanner.business.resources.entities.VirtualWorker;
 import org.navalplanner.business.resources.entities.Worker;
 import org.navalplanner.business.scenarios.entities.Scenario;
+import org.navalplanner.business.workingday.EffortDuration;
 import org.navalplanner.business.workingday.ResourcesPerDay;
 
 public class GenericResourceAllocationTest {
@@ -232,8 +233,9 @@ public class GenericResourceAllocationTest {
                     @Override
                     public Integer answer() throws Throwable {
                         ResourcesPerDay resourcesPerDay = (ResourcesPerDay) getCurrentArguments()[1];
-                        return resourcesPerDay
-                                .asHoursGivenResourceWorkingDayOf(hoursPerDay);
+                        return BaseCalendar.roundToHours(resourcesPerDay
+                                .asDurationGivenWorkingDayOf(EffortDuration
+                                        .hours(hoursPerDay)));
                     }
                 }).anyTimes();
         expect(baseCalendar.canWork(isA(LocalDate.class))).andReturn(true)
@@ -325,7 +327,8 @@ public class GenericResourceAllocationTest {
 
         List<GenericDayAssignment> orderedAssignmentsFor = genericResourceAllocation
                 .getOrderedAssignmentsFor(worker1);
-        int hoursPerDay = resourcesPerDay.asHoursGivenResourceWorkingDayOf(8);
+        int hoursPerDay = resourcesPerDay.asDurationGivenWorkingDayOf(
+                EffortDuration.hours(8)).getHours();
         assertThat(orderedAssignmentsFor, haveHours(hoursPerDay, hoursPerDay));
     }
 
@@ -347,7 +350,8 @@ public class GenericResourceAllocationTest {
 
         List<GenericDayAssignment> orderedAssignmentsFor = genericResourceAllocation
                 .getOrderedAssignmentsFor(worker1);
-        int hoursPerDay = resourcesPerDay.asHoursGivenResourceWorkingDayOf(8);
+        int hoursPerDay = resourcesPerDay.asDurationGivenWorkingDayOf(
+                EffortDuration.hours(8)).getHours();
         assertThat(orderedAssignmentsFor, haveHours(hoursPerDay, hoursPerDay));
     }
 
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/SpecificResourceAllocationTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/SpecificResourceAllocationTest.java
index 05a2cd1d8..9b336d0d2 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/SpecificResourceAllocationTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/entities/SpecificResourceAllocationTest.java
@@ -49,12 +49,13 @@ import org.junit.Test;
 import org.navalplanner.business.calendars.entities.AvailabilityTimeLine;
 import org.navalplanner.business.calendars.entities.BaseCalendar;
 import org.navalplanner.business.calendars.entities.ResourceCalendar;
+import org.navalplanner.business.planner.entities.ResourceAllocation.DetachDayAssignmentOnRemoval;
+import org.navalplanner.business.planner.entities.ResourceAllocation.IOnDayAssignmentRemoval;
 import org.navalplanner.business.planner.entities.SpecificDayAssignment;
 import org.navalplanner.business.planner.entities.SpecificResourceAllocation;
 import org.navalplanner.business.planner.entities.Task;
-import org.navalplanner.business.planner.entities.ResourceAllocation.DetachDayAssignmentOnRemoval;
-import org.navalplanner.business.planner.entities.ResourceAllocation.IOnDayAssignmentRemoval;
 import org.navalplanner.business.resources.entities.Worker;
+import org.navalplanner.business.workingday.EffortDuration;
 import org.navalplanner.business.workingday.ResourcesPerDay;
 
 public class SpecificResourceAllocationTest {
@@ -96,7 +97,9 @@ public class SpecificResourceAllocationTest {
             public Integer answer() throws Throwable {
                 ResourcesPerDay perDay = (ResourcesPerDay) EasyMock
                         .getCurrentArguments()[1];
-                return perDay.asHoursGivenResourceWorkingDayOf(hours);
+                return BaseCalendar.roundToHours(perDay
+                        .asDurationGivenWorkingDayOf(EffortDuration
+                                .hours(hours)));
             }
         };
     }
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/ResourcesPerDayTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/ResourcesPerDayTest.java
index c04dc808d..7fe6a653b 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/ResourcesPerDayTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/workingday/ResourcesPerDayTest.java
@@ -25,6 +25,9 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
+import static org.navalplanner.business.workingday.EffortDuration.hours;
+import static org.navalplanner.business.workingday.EffortDuration.seconds;
+import static org.navalplanner.business.workingday.EffortDuration.zero;
 
 import java.math.BigDecimal;
 
@@ -32,6 +35,8 @@ import org.hamcrest.BaseMatcher;
 import org.hamcrest.Description;
 import org.hamcrest.Matcher;
 import org.junit.Test;
+import org.navalplanner.business.workingday.EffortDuration;
+import org.navalplanner.business.workingday.EffortDuration.Granularity;
 import org.navalplanner.business.workingday.ResourcesPerDay;
 import org.navalplanner.business.workingday.ResourcesPerDay.ResourcesPerDayDistributor;
 
@@ -107,17 +112,43 @@ public class ResourcesPerDayTest {
     }
 
     @Test
-    public void canBeConvertedToHoursGivenTheWorkingDayHours() {
+    public void canBeConvertedToDurationsGivenTheWorkingDayInDifferentGranularities() {
         ResourcesPerDay units = ResourcesPerDay.amount(2);
-        assertThat(units.asHoursGivenResourceWorkingDayOf(8), equalTo(16));
+        for (Granularity each : Granularity.values()) {
+            assertThat(units.asDurationGivenWorkingDayOf(EffortDuration
+                    .elapsing(8, each)), equalTo(EffortDuration.elapsing(16,
+                    each)));
+        }
     }
 
     @Test
-    public void ifTheAmountIsDecimalTheRoundingIsHalfUp() {
-        ResourcesPerDay units = ResourcesPerDay.amount(new BigDecimal(2.4));
-        assertThat(units.asHoursGivenResourceWorkingDayOf(8), equalTo(19));
-        assertThat(units.asHoursGivenResourceWorkingDayOf(10), equalTo(24));
-        assertThat(units.asHoursGivenResourceWorkingDayOf(2), equalTo(5));
+    public void ifTheAmountIsDecimalTheSecondsAreMultiplied() {
+        ResourcesPerDay resourcesPerDay = ResourcesPerDay
+                .amount(new BigDecimal(2.4));
+        assertThat(resourcesPerDay.asDurationGivenWorkingDayOf(hours(8)),
+                equalTo(hours(19).and(12, Granularity.MINUTES)));
+        assertThat(resourcesPerDay.asDurationGivenWorkingDayOf(hours(10)),
+                equalTo(hours(24)));
+        assertThat(resourcesPerDay.asDurationGivenWorkingDayOf(hours(2)),
+                equalTo(hours(4).and(48, Granularity.MINUTES)));
+    }
+
+    @Test
+    public void theSecondsAreRoundedHalfUpUnlessItIsMinusThanOneSecond() {
+        ResourcesPerDay resourcesPerDay = ResourcesPerDay
+                .amount(new BigDecimal(2.4));
+        assertThat(resourcesPerDay.asDurationGivenWorkingDayOf(seconds(1)),
+                equalTo(seconds(2)));
+        assertThat(resourcesPerDay.asDurationGivenWorkingDayOf(seconds(2)),
+                equalTo(seconds(5)));
+    }
+
+    @Test
+    public void asSecondsMustReturnOneIfResultingAmountFromMultiplicationIsGreaterThanZero() {
+        ResourcesPerDay resourcesPerDay = ResourcesPerDay
+                .amount(new BigDecimal(0.1));
+        assertThat(resourcesPerDay.asDurationGivenWorkingDayOf(seconds(1)),
+                equalTo(seconds(1)));
     }
 
     @Test
@@ -128,19 +159,11 @@ public class ResourcesPerDayTest {
         assertEquals(a, b);
     }
 
-    @Test
-    public void asHoursMustReturnOneIfAmountIsGreaterThanZero() {
-        ResourcesPerDay amount = ResourcesPerDay.amount(new BigDecimal(0.05));
-        int hours = amount
-                .asHoursGivenResourceWorkingDayOf(8);
-        assertThat(hours, equalTo(1));
-    }
-
     @Test
     public void ifTheAmountIsZeroMustReturnZero() {
         ResourcesPerDay amount = ResourcesPerDay.amount(BigDecimal.ZERO);
-        int hours = amount.asHoursGivenResourceWorkingDayOf(8);
-        assertThat(hours, equalTo(0));
+        EffortDuration result = amount.asDurationGivenWorkingDayOf(hours(8));
+        assertThat(result, equalTo(zero()));
     }
 
     @Test