NSGregorianCalendarこの通知が土曜日にスケジュールされていない理由がわからないようです...との両方を試しましたautoupdatingCurrentCalendar。設定中です[dateComps setWeekday:7];が、日曜日に戻ってきます。
//NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar];
 NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *timeComponent = [calendar components:( NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit ) fromDate:reminderTime];
 // Set up the fire time
 NSDateComponents *dateComps = [[NSDateComponents alloc] init];
 [dateComps setYear: 2012];;
 [dateComps setHour: timeComponent.hour];
 [dateComps setMinute: timeComponent.minute];
 [dateComps setSecond:0];
 // Set day of the week
 [dateComps setWeekday:7];
 NSDate *itemDate = [calendar dateFromComponents:dateComps];
 UILocalNotification *notification = [[UILocalNotification alloc] init];
 if (notification == nil)
     return;
 notification.fireDate = itemDate;
 notification.repeatInterval = NSWeekCalendarUnit;