java - Alarm manager not working properly -

i sending msg using alarm manager, alarm not working.if time 18hrs , set alarm 8 hrs sends msg right @ time. here code.

public class time_picker extends appcompatactivity {     timepicker time_picker;     string tag="pritesh";     static alarmmanager[] alarmmanager=new alarmmanager[5];     static pendingintent[] pendingintent = new pendingintent[5];     edittext message;     edittext phone;     intent myintent;   //  alarmmanager alarmmanager;     //pendingintent pendingintent;     public static string phone;     public static string message;     public int i;     array ob=new array();     static arraylist<pendingintent> pendingarray=new arraylist<>(5);            public void setalarm(view view) {                  //      alarmmanager alarmmanager[]=new alarmmanager[5];  //          if(prevention.timer==0) {                 phone = phone.gettext().tostring();                 message = message.gettext().tostring();                 phone.settext("");                 message.settext("");                 //validating if field empty                 if (phone.length() >= 10 && message.length() > 0) {                     toast.maketext(this.getapplicationcontext(), "your sms sent soon", toast.length_short).show();                     //getting calender reference                     calendar cal = calendar.getinstance();                     int currentapiversion = android.os.build.version.sdk_int;                     if (currentapiversion > android.os.build.version_codes.lollipop_mr1) {                         cal.set(calendar.minute, time_picker.getminute());                         cal.set(calendar.hour_of_day, time_picker.gethour());                     } else {                         //setting date , time time picker                         cal.set(calendar.minute, time_picker.getcurrentminute());                         cal.set(calendar.hour_of_day, time_picker.getcurrenthour());                     }                     int = (calendar.getinstance().get(calendar.second) * 1000);                     i=array.select;                     myintent = new intent(this, myreceiver.class);                     myintent.putextra("pos",array.select);                     //pending intent sending intent afterwards                     pendingintent[array.select] = pendingintent.getbroadcast(this.getapplicationcontext(), array.select, myintent, 0);                     alarmmanager[array.select] = (alarmmanager) (this.getsystemservice(context.alarm_service));                     alarmmanager[array.select].set(alarmmanager.rtc, cal.gettimeinmillis() - a, pendingintent[array.select]);                      pendingarray.add(pendingintent[array.select]);                     sms_list.phone[array.select]=phone;                     intent = new intent(this, sms_list.class);                     back.putextra("phone", phone);                     back.putextra("flag",2);                     back.putextra("msg", message);                     back.putextra("hour", (int) cal.get(calendar.hour_of_day));                     back.putextra("min", (int) cal.get(calendar.minute));                      startactivity(back);                      //int b;                  }                 else                 {                     toast.maketext(this.getapplicationcontext(), "please fill details", toast.length_short).show();                     array.a[array.select]=false;                     ob.sort();                 }       } 

}

the code if set time has large difference doesnt work.

and can set alarm using 12 clock?

you cannot set alarm time passed.

 alarmmanager[array.select].set(alarmmanager.rtc, cal.gettimeinmillis() - a, pendingintent[array.select]); 

try future time below.

alarmmgr.set(alarmmanager.elapsed_realtime_wakeup,     systemclock.elapsedrealtime() +     60 * 1000, alarmintent);