android date tools and date picker for tree calendar systems Jalali , Hijri , Gregorian
primary color will be your theme color
copy this to "yourProject/app/libs" 
 have problem?
date converter: more here.
DateModel hijri = DateConverter.GregorianToHijri(2018, 1, 1);
//hijri.day;
//hijri.month;
//hijri.year;date picker: 
xml:(don't change height and width)
<com.ali.uneversaldatetools.datePicker.UDatePicker
        android:id="@+id/date_picker"
        android:layout_width="300dp"
        android:layout_height="350dp"/>java:
UDatePicker uDatePicker = findViewById(R.id.date_picker);
//push date to show in first time
uDatePicker.ShowDatePicker(dateSystem);
//or use current date
uDatePicker.ShowDatePicker(Calendar.Jalali);
//get on day selected event
uDatePicker.setOnDateSelected((dateSystem, unixTime) -> {
    //do something...
});
//or get date when ever you want
uDatePicker.getSelectedUnixTime();//as a unix time
uDatePicker.getSelectedDate();//as a DateSystem object1.persian 
2.english 
and its easy to add new language see
here.
under MIT licence


