servo sweep for specific time duration

servo_sweep_for_specific_time.ino

#include <Servo.h>
Servo myservo;
int pos = 0; 

void setup() {
  myservo.attach(9);
 Serial.begin(9600);

}
int jatin=2000;   // interval for which servo will sweep
unsigned long cm;   // current miliseconds
void loop() {
  myservo.write(0);     // setting servo pos at default
  cm=millis();          // starting measuring miliseconds
  if(cm<jatin)          // comparing elapsed miliseconds to interval
  {
  // servo sweep program start 
    for (pos = 0; pos <= 30; pos += 10) {
     myservo.write(pos);           
    delay(15);  
  }
  for (pos = 30; pos >= 0; pos -= 10) { 
    myservo.write(pos);              
    delay(15);                 
  }   // servo sweep program ends
  Serial.println(cm);     // println elapsed miliseconds
  }  
}