enter code here

void main(){
    ...
    //set alarm at 16:0:0 and trigger Event_1 at interrupt time
    rtc.enableAlarm(16,0,0);
    rtc.attachInterrupt(Event_1_isr);
    ...
}

void Event_1_isr()
{
    ...some code...
    //Set next alarm and interrupt Event_2
    rtc.setAlarmTime(16, 0, 15);
    rtc.enableAlarm(rtc.MATCH_HHMMSS);
    rtc.detachInterrupt();
    rtc.attachInterrupt(Event_2_isr);
}

void Event_2_isr(){
    ...some code...
    //I guess you get the point
    rtc.setAlarmTime(16, 0, 30);
    rtc.enableAlarm(rtc.MATCH_HHMMSS);
    rtc.detachInterrupt();
    rtc.attachInterrupt(Event_3_isr);
}