Waterin and lightning Random

Hi guys,
I want to water 5min and light 12hours my plant per day. The problem is that I want it random.
For example 2hours light, then shut down, then 1h32 light etc... the same for water.
I have an arduino nano with RTC DS3132 and two relays 220V and this is the code I used for the beginning.

#include <DS3231.h>

#include <Wire.h>

/*
  DS3231: Real-Time Clock. Alarm simple
  Read more: www.jarzebski.pl/arduino/komponenty/zegar-czasu-rzeczywistego-rtc-DS3231.html
  GIT: https://github.com/jarzebski/Arduino-DS3231
  Web: http://www.jarzebski.pl
  (c) 2014 by Korneliusz Jarzebski
*/




DS3231 clock;
RTCDateTime dt;
int led = 8;
int relay = 9;

void setup()
{
  Serial.begin(9600);
  
  // Initialize DS3231
  Serial.println("Initialize DS3231");;
  clock.begin();

  // Disarm alarms and clear alarms for this example, because alarms is battery backed.
  // Under normal conditions, the settings should be reset after power and restart microcontroller.
  clock.armAlarm1(false);
  clock.armAlarm2(false);
  clock.clearAlarm1();
  clock.clearAlarm2();

  pinMode(relay, OUTPUT);
  digitalWrite(relay, LOW);
  pinMode(led, OUTPUT);
  digitalWrite(led, LOW);
 
  // Manual (Year, Month, Day, Hour, Minute, Second)
 

  // Set Alarm - Every second.
  // DS3231_EVERY_SECOND is available only on Alarm1.
  // setAlarm1(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  // clock.setAlarm1(0, 0, 0, 0, DS3231_EVERY_SECOND);

  // Set Alarm - Every full minute.
  // DS3231_EVERY_MINUTE is available only on Alarm2.
  // setAlarm2(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  // clock.setAlarm2(0, 0, 0, 0, DS3231_EVERY_MINUTE);
  
  // Set Alarm1 - Every 20s in each minute
  // setAlarm1(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  clock.setAlarm1(0, 0, 0, 20, DS3231_MATCH_S);

  // Set Alarm2 - Every 01m in each hour
  // setAlarm2(Date or Day, Hour, Minute, Mode, Armed = true)
  clock.setAlarm2(0, 0, 1,     DS3231_MATCH_M);

  // Set Alarm - Every 01m:25s in each hour
  // setAlarm1(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  // clock.setAlarm1(0, 0, 1, 25, DS3231_MATCH_M_S);

  // Set Alarm - Every 01h:10m:30s in each day
  // setAlarm1(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  // clock.setAlarm1(0, 1, 10, 30, DS3231_MATCH_H_M_S);

  // Set Alarm - 07h:00m:00s in 25th day in month
  // setAlarm1(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  // clock.setAlarm1(25, 7, 0, 0, DS3231_MATCH_DT_H_M_S);

  // Set Alarm - 10h:45m:30s in every Friday (1 - Mon, 7 - Sun)
  // setAlarm1(Date or Day, Hour, Minute, Second, Mode, Armed = true)
  // clock.setAlarm1(5, 10, 40, 30, DS3231_MATCH_DY_H_M_S);
  
  // Check alarm settings
  checkAlarms();
}

void checkAlarms()
{
  RTCAlarmTime a1;  
  RTCAlarmTime a2;

  if (clock.isArmed1())
  {
    a1 = clock.getAlarm1();

    Serial.print("Alarm1 is triggered ");
    switch (clock.getAlarmType1())
    {
      case DS3231_EVERY_SECOND:
        Serial.println("every second");
        break;
      case DS3231_MATCH_S:
        Serial.print("when seconds match: ");
        Serial.println(clock.dateFormat("__ __:__:s", a1));
        break;
      case DS3231_MATCH_M_S:
        Serial.print("when minutes and sencods match: ");
        Serial.println(clock.dateFormat("__ __:i:s", a1));
        break;
      case DS3231_MATCH_H_M_S:
        Serial.print("when hours, minutes and seconds match: ");
        Serial.println(clock.dateFormat("__ H:i:s", a1));
        break;
      case DS3231_MATCH_DT_H_M_S:
        Serial.print("when date, hours, minutes and seconds match: ");
        Serial.println(clock.dateFormat("d H:i:s", a1));
        break;
      case DS3231_MATCH_DY_H_M_S:
        Serial.print("when day of week, hours, minutes and seconds match: ");
        Serial.println(clock.dateFormat("l H:i:s", a1));
        break;
      default: 
        Serial.println("UNKNOWN RULE");
        break;
    }
  } else
  {
    Serial.println("Alarm1 is disarmed.");
  }

  if (clock.isArmed2())
  {
    a2 = clock.getAlarm2();

    Serial.print("Alarm2 is triggered ");
    switch (clock.getAlarmType2())
    {
      case DS3231_EVERY_MINUTE:
        Serial.println("every minute");
        break;
      case DS3231_MATCH_M:
        Serial.print("when minutes match: ");
        Serial.println(clock.dateFormat("__ __:i:s", a2));
        break;
      case DS3231_MATCH_H_M:
        Serial.print("when hours and minutes match:");
        Serial.println(clock.dateFormat("__ H:i:s", a2));
        break;
      case DS3231_MATCH_DT_H_M:
        Serial.print("when date, hours and minutes match: ");
        Serial.println(clock.dateFormat("d H:i:s", a2));
        break;
      case DS3231_MATCH_DY_H_M:
        Serial.println("when day of week, hours and minutes match: ");
        Serial.print(clock.dateFormat("l H:i:s", a2));
        break;
      default: 
        Serial.println("UNKNOWN RULE"); 
        break;
    }
  } else
  {
    Serial.println("Alarm2 is disarmed.");
  }
}

void loop()
{
  dt = clock.getDateTime();

  Serial.println(clock.dateFormat("d-m-Y H:i:s - l", dt));

  // Call isAlarm1(false) if you want clear alarm1 flag manualy by clearAlarm1();
  if (clock.isAlarm1())
  {
    Serial.println("ALARM 1 TRIGGERED!");
    digitalWrite(led, HIGH);
    delay(5000);
    digitalWrite(relay, HIGH);
    delay(1000);
   
  }
  else 
digitalWrite(led, LOW);
digitalWrite(relay, LOW);

  // Call isAlarm2(false) if you want clear alarm1 flag manualy by clearAlarm2();
  if (clock.isAlarm2())
  {
    Serial.println("ALARM 2 TRIGGERED!");
    
 }
 
  delay(1000);
}

Hi,
You have posted on the wrong part of the forum. You are on its french part.
Either you write in french or you ask moderator to move your post to the english part of the forum.