diff --git a/app/src/main/java/org/tasks/caldav/CaldavSynchronizer.java b/app/src/main/java/org/tasks/caldav/CaldavSynchronizer.java
index b1d40fba1..1c508249d 100644
--- a/app/src/main/java/org/tasks/caldav/CaldavSynchronizer.java
+++ b/app/src/main/java/org/tasks/caldav/CaldavSynchronizer.java
@@ -92,15 +92,7 @@ public class CaldavSynchronizer {
     this.client = client;
   }
 
-  public void sync() {
-    // required for dav4android (ServiceLoader)
-    Thread.currentThread().setContextClassLoader(context.getClassLoader());
-    for (CaldavAccount account : caldavDao.getAccounts()) {
-      sync(account);
-    }
-  }
-
-  private void sync(CaldavAccount account) {
+  public void sync(CaldavAccount account) {
     if (!inventory.hasPro()) {
       setError(account, context.getString(R.string.requires_pro_subscription));
       return;
diff --git a/app/src/main/java/org/tasks/gtasks/GoogleTaskSynchronizer.java b/app/src/main/java/org/tasks/gtasks/GoogleTaskSynchronizer.java
index 292dd2cca..2d8cde856 100644
--- a/app/src/main/java/org/tasks/gtasks/GoogleTaskSynchronizer.java
+++ b/app/src/main/java/org/tasks/gtasks/GoogleTaskSynchronizer.java
@@ -131,29 +131,25 @@ public class GoogleTaskSynchronizer {
     }
   }
 
-  public void sync() {
-    List<GoogleTaskAccount> accounts = googleTaskListDao.getAccounts();
-    for (int i = 0; i < accounts.size(); i++) {
-      GoogleTaskAccount account = accounts.get(i);
-      Timber.d("%s: start sync", account);
-      try {
-        if (i == 0 || inventory.hasPro()) {
-          synchronize(account);
-          account.setError("");
-        } else {
-          account.setError(context.getString(R.string.requires_pro_subscription));
-        }
-      } catch (UserRecoverableAuthIOException e) {
-        Timber.e(e);
-        sendNotification(context, e.getIntent());
-      } catch (Exception e) {
-        account.setError(e.getMessage());
-        tracker.reportException(e);
-      } finally {
-        googleTaskListDao.update(account);
-        localBroadcastManager.broadcastRefreshList();
-        Timber.d("%s: end sync", account);
+  public void sync(GoogleTaskAccount account, int i) {
+    Timber.d("%s: start sync", account);
+    try {
+      if (i == 0 || inventory.hasPro()) {
+        synchronize(account);
+        account.setError("");
+      } else {
+        account.setError(context.getString(R.string.requires_pro_subscription));
       }
+    } catch (UserRecoverableAuthIOException e) {
+      Timber.e(e);
+      sendNotification(context, e.getIntent());
+    } catch (Exception e) {
+      account.setError(e.getMessage());
+      tracker.reportException(e);
+    } finally {
+      googleTaskListDao.update(account);
+      localBroadcastManager.broadcastRefreshList();
+      Timber.d("%s: end sync", account);
     }
   }
 
@@ -220,7 +216,8 @@ public class GoogleTaskSynchronizer {
     }
     if (preferences.isPositionHackEnabled()) {
       for (TaskList list : gtaskLists) {
-        List<com.google.api.services.tasks.model.Task> tasks = fetchPositions(gtasksInvoker, list.getId());
+        List<com.google.api.services.tasks.model.Task> tasks =
+            fetchPositions(gtasksInvoker, list.getId());
         for (com.google.api.services.tasks.model.Task task : tasks) {
           googleTaskDao.updatePosition(task.getId(), task.getParent(), task.getPosition());
         }
@@ -230,8 +227,8 @@ public class GoogleTaskSynchronizer {
     account.setEtag(eTag);
   }
 
-  private List<com.google.api.services.tasks.model.Task> fetchPositions(GtasksInvoker gtasksInvoker, String listId)
-      throws IOException {
+  private List<com.google.api.services.tasks.model.Task> fetchPositions(
+      GtasksInvoker gtasksInvoker, String listId) throws IOException {
     List<com.google.api.services.tasks.model.Task> tasks = new ArrayList<>();
     String nextPageToken = null;
     do {
diff --git a/app/src/main/java/org/tasks/jobs/SyncWork.java b/app/src/main/java/org/tasks/jobs/SyncWork.java
index 9772b60b8..60963208e 100644
--- a/app/src/main/java/org/tasks/jobs/SyncWork.java
+++ b/app/src/main/java/org/tasks/jobs/SyncWork.java
@@ -1,12 +1,22 @@
 package org.tasks.jobs;
 
+import static com.todoroo.andlib.utility.AndroidUtilities.atLeastJellybeanMR1;
+import static java.util.concurrent.Executors.newFixedThreadPool;
+
 import android.content.Context;
 import androidx.annotation.NonNull;
 import androidx.work.WorkerParameters;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
 import javax.inject.Inject;
 import org.tasks.LocalBroadcastManager;
 import org.tasks.analytics.Tracker;
 import org.tasks.caldav.CaldavSynchronizer;
+import org.tasks.data.CaldavAccount;
+import org.tasks.data.CaldavDao;
+import org.tasks.data.GoogleTaskAccount;
+import org.tasks.data.GoogleTaskListDao;
 import org.tasks.gtasks.GoogleTaskSynchronizer;
 import org.tasks.injection.InjectingWorker;
 import org.tasks.injection.JobComponent;
@@ -21,6 +31,8 @@ public class SyncWork extends InjectingWorker {
   @Inject LocalBroadcastManager localBroadcastManager;
   @Inject Preferences preferences;
   @Inject Tracker tracker;
+  @Inject CaldavDao caldavDao;
+  @Inject GoogleTaskListDao googleTaskListDao;
 
   public SyncWork(@NonNull Context context, @NonNull WorkerParameters workerParams) {
     super(context, workerParams);
@@ -38,8 +50,20 @@ public class SyncWork extends InjectingWorker {
     preferences.setSyncOngoing(true);
     localBroadcastManager.broadcastRefresh();
     try {
-      caldavSynchronizer.sync();
-      googleTaskSynchronizer.sync();
+      int numThreads = atLeastJellybeanMR1() ? Runtime.getRuntime().availableProcessors() : 2;
+      ExecutorService executor = newFixedThreadPool(numThreads);
+
+      for (CaldavAccount account : caldavDao.getAccounts()) {
+        executor.execute(() -> caldavSynchronizer.sync(account));
+      }
+      List<GoogleTaskAccount> accounts = googleTaskListDao.getAccounts();
+      for (int i = 0; i < accounts.size(); i++) {
+        int count = i;
+        executor.execute(() -> googleTaskSynchronizer.sync(accounts.get(count), count));
+      }
+
+      executor.shutdown();
+      executor.awaitTermination(15, TimeUnit.MINUTES);
     } catch (Exception e) {
       tracker.reportException(e);
     } finally {