RTClib library the second, second I'm using RTClib for my DS3231 module, the problem is the library is displaying the second without zero behind it: 22:1:1 and when i print the time on my 16x2 LCD time is displaying like this:


  22:22:59
  
  22:23:19
  
  22:23:29
  
  ...
  
  22:23:59
  
  22:23:10
  
  22:23:11


the second number of seconds is not getting cleared.
i know one solution to this is to use lcd.clear() function to update the LCD in each loop but is there any other way to clear that second number or do something so library show zero behind second?
It's your responsibility to format the time properly, not the library. The library just gives you a number. If you want a leading zero then it's up to you to provide that leading zero.

For example:

if (now.seconds() &lt; 10) {
    lcd.print("0");
}
lcd.print(now.seconds());


Or:

char timestr[9];
snprintf(timestr, 9, "%02d:%02d:%02d", now.hours(), now.seconds(), now.minutes());
lcd.print(timestr);