using Liferay Localization is not enough to use localized calendar systems(Calendar systems like Japanese or Hijri(Persian)Calendar, not just translating Georgian calendar to other languages). so I decide to make liferay to use other Calendar systems(changing in Portal Source Code or using Ext Plugin). as Liferay use JDK Calendar standard and extending JDK default Calendar system to implement a new Calendar like Hijri is almost impossible, the new idea is changing liferay to use another Calendar liberaries like Joda-Time(which has a great power for localization).
I summarize my solution to use custom Calendar Systems:

changing the CalendarFactory Service API for changing method signature to use Joda-Time Classes instead of java.util.Calendar
implement new CalendarFactoryImpl
correcting all the side-effect Errors(couse they expect java.util.Calendar not org.joda.time.DateTime)

I have two Question.
1. am I correct in this path?
2.how can I use Ext Plugin to change the Core Service API, I mean changin the CalendarFactory/Util interfaces (change return types...)and manage other side-effects?

It's not that's simple. You'll also have to modify AlloyUI's calendar to change the popup calendar.

it seems you'r right. yes I should change AlloyUI Component too, but I didn't get my answer

You'll just want to change how calendar is presented to the user instead of how dates are kept in the system. That is, you'll want to wrap the liferay's calendar system instead of modifying it. Have your presentation layer call your wrapper methods instead of liferay.