add some navigation between activities

app/src/main/AndroidManifest.xml

@@ -31,19 +31,23 @@
 
         <activity
             android:name=".activities.AboutActivity"
-            android:label="@string/about"/>
+            android:label="@string/about"
+            android:parentActivityName=".activities.MainActivity"/>
 
         <activity
             android:name=".activities.DayActivity"
-            android:label="@string/details"/>
+            android:label="@string/details"
+            android:parentActivityName=".activities.MainActivity"/>
 
         <activity
             android:name=".activities.EventActivity"
-            android:label="@string/event"/>
+            android:label="@string/event"
+            android:parentActivityName=".activities.DayActivity"/>
 
         <activity
             android:name=".activities.LicenseActivity"
-            android:label="@string/third_party_licences"/>
+            android:label="@string/third_party_licences"
+            android:parentActivityName=".activities.AboutActivity"/>
 
         <activity
             android:name=".activities.SettingsActivity"

app/src/main/java/com/simplemobiletools/calendar/activities/DayActivity.java

@@ -124,6 +124,7 @@ public class DayActivity extends SimpleActivity
         datePicker.init(dateTime.getYear(), dateTime.getMonthOfYear() - 1, dateTime.getDayOfMonth(), null);
 
         alertDialog.setView(view);
+        alertDialog.setNegativeButton("Cancel", null);
         alertDialog.setPositiveButton("OK", new DialogInterface.OnClickListener() {
             public void onClick(DialogInterface dialog, int id) {
                 final int month = datePicker.getMonth() + 1;

app/src/main/java/com/simplemobiletools/calendar/activities/SimpleActivity.java

@@ -3,6 +3,7 @@ package com.simplemobiletools.calendar.activities;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.v7.app.AppCompatActivity;
+import android.view.MenuItem;
 
 import com.simplemobiletools.calendar.Config;
 import com.simplemobiletools.calendar.R;
@@ -16,4 +17,15 @@ public class SimpleActivity extends AppCompatActivity {
         setTheme(mConfig.getIsDarkTheme() ? R.style.AppTheme_Dark : R.style.AppTheme);
         super.onCreate(savedInstanceState);
     }
+
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        switch (item.getItemId()) {
+            case android.R.id.home:
+                finish();
+                return true;
+            default:
+                return super.onOptionsItemSelected(item);
+        }
+    }
 }