Try like below code:

date_time_layout.xml

<DatePicker
    android:id="@+id/datePicker1"
    android:layout_width="wrap_content"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:calendarViewShown="false" > <!-- style="@style/date_picker_style" -->
</DatePicker>

<TimePicker
    android:id="@+id/timePicker1"
    android:layout_width="wrap_content"
    android:layout_height="0dp"
    android:layout_weight="1" >
</TimePicker>

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="10dp"
    android:layout_marginLeft="5dp"
    android:layout_marginRight="5dp" >

    <Button
        android:id="@+id/btnCancelDT"
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:background="@drawable/button_selector"
        android:text="Cancel"
        android:textColor="@color/white"
        android:textStyle="bold" />

    <Button
        android:id="@+id/btnSetDT"
        android:layout_width="0dip"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:background="@drawable/button_selector"
        android:text="Set"
        android:textColor="@color/white"
        android:textStyle="bold" />
</LinearLayout>

Activity class:

public void showDateTimePickerDialog() {


        final Dialog dialog = new Dialog(this);

        dialog.setContentView(R.layout.date_time_layout);

        dialog.setTitle("Set Schedule Call");

        dialog.show();

        Button btnCancel = (Button)dialog.findViewById(R.id.btnCancelDT);
        Button btnSet = (Button)dialog.findViewById(R.id.btnSetDT);

        final DatePicker dp = (DatePicker)dialog.findViewById(R.id.datePicker1);
        final TimePicker tp = (TimePicker)dialog.findViewById(R.id.timePicker1);


        btnCancel.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                dialog.dismiss();
            }
        });

        btnSet.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                String am_pm = "";
                // TODO Auto-generated method stub
                int m = dp.getMonth()+1;
                int d = dp.getDayOfMonth();
                int y = dp.getYear();

                int h = tp.getCurrentHour();
                int min = tp.getCurrentMinute();

                String strm = String.valueOf(min);

                if(strm.length()==1){
                    strm = "0"+strm;
                }
                if(h>12){
                    am_pm = "PM";
                    h = h-12;
                }else{
                    am_pm = "AM";
                }

                date = m+"/"+d+"/"+y+" "+h+":"+strm+":00 "+am_pm;
                time = h+":"+strm+" "+am_pm;

                            System.out.println("Date: " + date +" Time: "+ time);

                dialog.dismiss();
            }
        });
    }

call this method on button click or as you want.

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Not sure what you are trying to do - especially the addClick (am not sure this onClick for DatePicker or any other button). Anyways, look at following two things:

1. Move initializing name and datePicker (make it class level) to onCreate.
2. Override toString() in Friend class as well, if not done.

Try this code:

public class AddActivity extends ActionBarActivity {

private int year;
private int month;
private int day;
private String name;
private boolean isOK = false;
GregorianCalendar gregCal;
Date date;
FriendList friendlist;
Friend friend;
EditText text;
CharSequence charSequence;

DatePicker datepick;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_add);

    text = (EditText) findViewById(R.id.namefield);


    datepick = (DatePicker) findViewById(R.id.datePicker1);


}

public void checkFriend() {
    boolean duplicate = false;
    for (int i = 0; i < friendlist.getList().size(); i++) {

        if (friendlist.getList().get(i).equals(friend) == true) {
            duplicate = true;
        }
    }
    if (name == null) {
        charSequence = (CharSequence) "Name is empty!";
        Toast.makeText(this, charSequence, Toast.LENGTH_SHORT);

    }
    if (day == 0) {
        charSequence = (CharSequence) "Not a valid day!";
        Toast.makeText(this, charSequence, Toast.LENGTH_SHORT);
    }
    if (month == 0) {
        charSequence = (CharSequence) "Not a valid month!";
        Toast.makeText(this, charSequence, Toast.LENGTH_SHORT);
    }
    if (year == 0) {
        charSequence = (CharSequence) "Not a valid year!";
        Toast.makeText(this, charSequence, Toast.LENGTH_SHORT);
    } else if (duplicate == true) {

        Toast.makeText(this, "This person already added",
                Toast.LENGTH_SHORT).show();
        isOK = false;

    } else {
        isOK = true;
    }
}

public void test(View view) {
    Toast.makeText(this, "testing", Toast.LENGTH_SHORT).show();
}

public void addClick(View view) {

    name = text.getText().toString();
    day = datepick.getDayOfMonth();
    month = datepick.getMonth();
    year = datepick.getYear();
    friend = new Friend(name, day, month, year);
    friendlist = FriendList.getInstance();
    // the toast is to check if the object is added correctly
    Toast.makeText(this, friend.toString(), Toast.LENGTH_LONG).show();
    checkFriend();
    if (isOK == true) {
        friendlist.addFriend(new Friend(name, day, month, year));
        finish();
    }
}

// This is the original code of the adding process, i attempted to re-do it
// to try and see if that could help me solve the problem
// public void saveBirthday(View view){
// text = (EditText)findViewById(R.id.namefield);
//
// DatePicker datePick = (DatePicker)findViewById(R.id.datePicker1);
// name = findViewById(R.id.namefield).toString();
// day = datePick.getDayOfMonth();
// month = datePick.getMonth();
// year = datePick.getYear();
// fl = FriendList.getInstance();
// friend = new Friend(name,day,month,year);
// Toast.makeText(this, friend.toString(), 3).show();
// checkFriend();
// if(isOK==true){
// fl.addFriend(friend);
// finish();
// }
//
//
// }
}

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try this like :

public class DatePickerFixedDates extends Activity {    

    final Calendar calender = Calendar.getInstance();
    int maxYear = calender.get(Calendar.YEAR);
    int maxMonth = calender.get(Calendar.MONTH);
    int maxDay = calender.get(Calendar.DAY_OF_MONTH);

    int minYear = 2004;
    int minMonth = 10; 
    int minDay = 25;
    private Button btn;
    private  DatePicker BirthDateDP;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.datepickerfixeddates);
        BirthDateDP = (DatePicker) findViewById(R.id.datepicker);
        btn = (Button) findViewById(R.id.button1);        
        btn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {       
                int day = BirthDateDP.getDayOfMonth();
                int month = BirthDateDP.getMonth();
                int year = BirthDateDP.getYear();           
            }
        });

        BirthDateDP.init(maxYear , maxMonth, maxDay, new OnDateChangedListener() {

            public void onDateChanged(DatePicker view, int year, int monthOfYear, int dayOfMonth)
            {           

                if (year < minYear)
                    view.updateDate(minYear, minMonth, minDay);

                    if (monthOfYear < minMonth && year == minYear)
                    view.updateDate(minYear, minMonth, minDay);

                    if (dayOfMonth < minDay && year == minYear && monthOfYear == minMonth)
                    view.updateDate(minYear, minMonth, minDay);


                    if (year > maxYear)
                    view.updateDate(maxYear, maxMonth, maxDay);

                    if (monthOfYear > maxMonth && year == maxYear)
                    view.updateDate(maxYear, maxMonth, maxDay);

                    if (dayOfMonth > maxDay && year == maxYear && monthOfYear == maxMonth)
                    view.updateDate(maxYear, maxMonth, maxDay);
            }
        });        
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
}

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Forget about strings, and go directly with the values:

DatePicker dp = (DatePicker) findViewById...
TimePicker tp = (TimePicker) findViewById...

Date timeStamp = new Date( dp.getYear(), dp.getMonth(), dp.getDay(), tp.getHour(), tp.getMinute(), 0 );

long longTime = timeStamp.getTime();

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you should use the broadcast reciever for this purpose and from there on you can trigger your service.

  int Hour = Time_Picker.getCurrentHour();
                    int Minute = Time_Picker.getCurrentMinute();

                DatePicker Date_Picker = (DatePicker)findViewById(R.id.datePicker1);
                int day = Date_Picker.getDayOfMonth();
                 int month = Date_Picker.getMonth() + 1;
                 int year = Date_Picker.getYear();


                Intent myIntent = new Intent(ScheduleMessage.this, recieve.class);

                Bundle bundle = new Bundle();
                         bundle.putCharSequence("Number", Number.getText().toString());
                         bundle.putCharSequence("Message", Message.getText().toString());
                         myIntent.putExtras(bundle);

                pendingIntent = PendingIntent.getBroadcast(ScheduleMessage.this, 0, myIntent, 0);

AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);

                 Calendar calendar = Calendar.getInstance();
                 calendar.setTimeInMillis(System.currentTimeMillis());
                 //calendar.add(Calendar.SECOND, 10);
                 calendar.set(year, month, day, Hour, Minute);

                 alarmManager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);

                         Toast.makeText(ScheduleMessage.this,"Start Alarm with \n" + 
                         "smsNumber = " + Number.getText().toString() + 
                         "\n" + "smsText = " + Message.getText().toString() + "\nScheduled for :"
                         + Hour +" "+Minute,
                           Toast.LENGTH_LONG).show();

This code will set the alarm which will trigger your Broadcast reciever. now in onRecieve function of your reciever call your service.

public class mainRecieve extends BroadcastReceiver{

    @Override
    public void onReceive(Context arg0, Intent arg1) {
        // TODO Auto-generated method stub

        try {

                    Intent ii=new Intent(arg0,MyAlarmService.class);
                    arg0.startService(ii);
                }               
                }
             catch (Exception e) {
                Toast.makeText(arg0, "There was an error somewhere, but we still received an alarm"+e, Toast.LENGTH_LONG).show();
                e.printStackTrace();
            }
    }

}

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