Shoutbox

You need to create it for yourself. Create a new String in your Preferences called ChatLogTimeStampFormat and  give it a value of HH':'mm':'ss for 24 hour clock or hh':mm':'ss tt for 12 hour clock with AM or PM. .

More info on these values-
Date Tags
To add normal text, use single quotes. Example: "dd'/'MM" will produce "18/10".

• d - Day of month as digits with no leading zero for single-digit days.
  
• dd - Day of month as digits with leading zero for single-digit days.
  
• ddd - Day of week as a three-letter abbreviation.
  
• dddd - Day of week as its full name.
  
• M - Month as digits with no leading zero for single-digit months.
  
• MM - Month as digits with leading zero for single-digit months.
  
• MMM - Month as a three-letter abbreviation.
  
• MMMM - Month as its full name.
  
• yy - Year as last two digits, but with leading zero for years less than 10.
  
• yyyy - Year represented by full four digits.

Time Tags
To add normal text, use single quotes. Example: "HH':'mm" will produce "12:40".

• h - Hours with no leading zero for single-digit hours; 12-hour clock.
  
• hh - Hours with leading zero for single-digit hours; 12-hour clock.
  
• H - Hours with no leading zero for single-digit hours; 24-hour clock.
  
• HH - Hours with leading zero for single-digit hours; 24-hour clock.
  
• m - Minutes with no leading zero for single-digit minutes.
  
• mm - Minutes with leading zero for single-digit minutes.
  
• s - Seconds with no leading zero for single-digit seconds.
  
• ss - Seconds with leading zero for single-digit seconds.
  
• t - One character time-marker string, such as A or P.
  
• tt - Multicharacter time-marker string, such as AM or PM.