How to schedule batch class based on country in Salesforce?

ust saving the class does not schedule it. You still need to tell the DB to schedule it. I generally write a schedule function within my class so that I can easily call it in one line, that uses my static chron string within the class. Something like this should work

global class Scheduler_class implements Schedulable{

public static String sched = '0 00 00 * * ?'; //Every Day at Midnight

global static String scheduleMe() {
Scheduler_class SC = new Scheduler_class();
return System.schedule('My batch Job', sched, SC);
}

global void execute(SchedulableContext sc) {

batchAUpdate_based_on_stage b1 = new batchAUpdate_based_on_stage();
ID batchprocessid = Database.executeBatch(b1,50);
}
}
The you just need to run Scheduler_class.scheduleMe(); from execute anonymous and it will be scheduled to run at your interval. This is important as this tells the DB to actually schedule it.